"""
セグメント木で行きたいところだけど、集合の管理が必要になるため、時間がかかりすぎてしまう。
と思いきや、文字の種類は26種類しかないので、問題ない。
"""
def main():
    import sys
    input = sys.stdin.readline
    from collections import Counter
    class BIT:
        def __init__(self,n):
            self.size = n
            self.tree = [Counter([]) for _ in range(n+1)]
        
        def change(self,i,x,y):
            while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
        def sum(self,i):
            s = Counter([])
            while i > 0:
                s += self.tree[i]
                i -= i&-i
            cnt = 0
            return s


    N = int(input())
    S = list(input())
    Q = int(input())
    bit = BIT(N)
    for i in range(N):
        bit.change(i+1," ",S[i])

    for _ in range(Q):
        q,a,b = input().split()
        if q == "1":
            x = S[int(a)-1]
            S[int(a)-1] = b
            bit.change(int(a),x,b)
        else:
            a = int(a)
            b = int(b)
            count = bit.sum(b) - bit.sum(a-1)
            ans = 0
            for v in count.values():
                if v > 0:
                    ans += 1
            print(ans)
main() """
セグメント木で行きたいところだけど、集合の管理が必要になるため、時間がかかりすぎてしまう。
と思いきや、文字の種類は26種類しかないので、問題ない。
""" def main():
    import sys
    input = sys.stdin.readline
    from collections import Counter
    class BIT:
        def __init__(self,n):
            self.size = n
            self.tree = [Counter([]) for _ in range(n+1)]
        
        def change(self,i,x,y):
            while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
        def sum(self,i):
            s = Counter([])
            while i > 0:
                s += self.tree[i]
                i -= i&-i
            cnt = 0
            return s


    N = int(input())
    S = list(input())
    Q = int(input())
    bit = BIT(N)
    for i in range(N):
        bit.change(i+1," ",S[i])

    for _ in range(Q):
        q,a,b = input().split()
        if q == "1":
            x = S[int(a)-1]
            S[int(a)-1] = b
            bit.change(int(a),x,b)
        else:
            a = int(a)
            b = int(b)
            count = bit.sum(b) - bit.sum(a-1)
            ans = 0
            for v in count.values():
                if v > 0:
                    ans += 1
            print(ans) main import sys sys input = sys.stdin.readline input sys.stdin.readline sys.stdin sys stdin readline from collections import Counter class BIT:
        def __init__(self,n):
            self.size = n
            self.tree = [Counter([]) for _ in range(n+1)]
        
        def change(self,i,x,y):
            while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
        def sum(self,i):
            s = Counter([])
            while i > 0:
                s += self.tree[i]
                i -= i&-i
            cnt = 0
            return s


     BIT def __init__(self,n):
            self.size = n
            self.tree = [Counter([]) for _ in range(n+1)]
        
         __init__ self.size = n self.size self size n Counter([]) for _ in range(n+1) for _ in range(n+1) _ range(n+1) range n+1 n 1 for _ in range(n+1) Counter([]) Counter [] self.tree = [Counter([]) for _ in range(n+1)] self.tree self tree [Counter([]) for _ in range(n+1)] self self n n def change(self,i,x,y):
            while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
         change while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
         i <= self.size i self.size self size if x in self.tree[i]:
                    self.tree[i][x] -= 1
                 x in self.tree[i] x self.tree[i] self.tree self tree i self.tree[i][x] -= 1 self.tree[i][x] self.tree[i] self.tree self tree i x 1 if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                 y not in self.tree[i] y self.tree[i] self.tree self tree i self.tree[i][y] = 1 self.tree[i][y] self.tree[i] self.tree self tree i y 1 self.tree[i][y] += 1 self.tree[i][y] self.tree[i] self.tree self tree i y 1 i += i&-i i i&-i i -i i self self i i x x y y def sum(self,i):
            s = Counter([])
            while i > 0:
                s += self.tree[i]
                i -= i&-i
            cnt = 0
            return s


     sum s = Counter([]) s Counter([]) Counter [] while i > 0:
                s += self.tree[i]
                i -= i&-i
             i > 0 i 0 s += self.tree[i] s self.tree[i] self.tree self tree i i -= i&-i i i&-i i -i i cnt = 0 cnt 0 return s s self self i i N = int(input()) N int(input()) int input() input S = list(input()) S list(input()) list input() input Q = int(input()) Q int(input()) int input() input bit = BIT(N) bit BIT(N) BIT N for i in range(N):
        bit.change(i+1," ",S[i])

     i range(N) range N bit.change(i+1," ",S[i]) bit.change bit change i+1 i 1 " " S[i] S i for _ in range(Q):
        q,a,b = input().split()
        if q == "1":
            x = S[int(a)-1]
            S[int(a)-1] = b
            bit.change(int(a),x,b)
        else:
            a = int(a)
            b = int(b)
            count = bit.sum(b) - bit.sum(a-1)
            ans = 0
            for v in count.values():
                if v > 0:
                    ans += 1
            print(ans) _ range(Q) range Q q,a,b = input().split() q input().split() ().split () input split a b if q == "1":
            x = S[int(a)-1]
            S[int(a)-1] = b
            bit.change(int(a),x,b)
        else:
            a = int(a)
            b = int(b)
            count = bit.sum(b) - bit.sum(a-1)
            ans = 0
            for v in count.values():
                if v > 0:
                    ans += 1
            print(ans) q == "1" q "1" x = S[int(a)-1] x S[int(a)-1] S int(a)-1 int(a) int a 1 S[int(a)-1] = b S[int(a)-1] S int(a)-1 int(a) int a 1 b bit.change(int(a),x,b) bit.change bit change int(a) int a x b a = int(a) a int(a) int a b = int(b) b int(b) int b count = bit.sum(b) - bit.sum(a-1) count bit.sum(b) - bit.sum(a-1) bit.sum(b) bit.sum bit sum b bit.sum(a-1) bit.sum bit sum a-1 a 1 ans = 0 ans 0 for v in count.values():
                if v > 0:
                    ans += 1
             v count.values() count.values count values if v > 0:
                    ans += 1
             v > 0 v 0 ans += 1 ans 1 print(ans) print ans main() main def main():
    import sys
    input = sys.stdin.readline
    from collections import Counter
    class BIT:
        def __init__(self,n):
            self.size = n
            self.tree = [Counter([]) for _ in range(n+1)]
        
        def change(self,i,x,y):
            while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
        def sum(self,i):
            s = Counter([])
            while i > 0:
                s += self.tree[i]
                i -= i&-i
            cnt = 0
            return s


    N = int(input())
    S = list(input())
    Q = int(input())
    bit = BIT(N)
    for i in range(N):
        bit.change(i+1," ",S[i])

    for _ in range(Q):
        q,a,b = input().split()
        if q == "1":
            x = S[int(a)-1]
            S[int(a)-1] = b
            bit.change(int(a),x,b)
        else:
            a = int(a)
            b = int(b)
            count = bit.sum(b) - bit.sum(a-1)
            ans = 0
            for v in count.values():
                if v > 0:
                    ans += 1
            print(ans) def main():
    import sys
    input = sys.stdin.readline
    from collections import Counter
    class BIT:
        def __init__(self,n):
            self.size = n
            self.tree = [Counter([]) for _ in range(n+1)]
        
        def change(self,i,x,y):
            while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
        def sum(self,i):
            s = Counter([])
            while i > 0:
                s += self.tree[i]
                i -= i&-i
            cnt = 0
            return s


    N = int(input())
    S = list(input())
    Q = int(input())
    bit = BIT(N)
    for i in range(N):
        bit.change(i+1," ",S[i])

    for _ in range(Q):
        q,a,b = input().split()
        if q == "1":
            x = S[int(a)-1]
            S[int(a)-1] = b
            bit.change(int(a),x,b)
        else:
            a = int(a)
            b = int(b)
            count = bit.sum(b) - bit.sum(a-1)
            ans = 0
            for v in count.values():
                if v > 0:
                    ans += 1
            print(ans) main
"""
セグメント木で行きたいところだけど、集合の管理が必要になるため、時間がかかりすぎてしまう。
と思いきや、文字の種類は26種類しかないので、問題ない。
"""
def main():
    import sys
    input = sys.stdin.readline
    from collections import Counter
    class BIT:
        def __init__(self,n):
            self.size = n
            self.tree = [Counter([]) for _ in range(n+1)]
        
        def change(self,i,x,y):
            while i <= self.size:
                if x in self.tree[i]:
                    self.tree[i][x] -= 1
                if y not in self.tree[i]:
                    self.tree[i][y] = 1
                else:
                    self.tree[i][y] += 1
                i += i&-i
    
        def sum(self,i):
            s = Counter([])
            while i > 0:
                s += self.tree[i]
                i -= i&-i
            cnt = 0
            return s


    N = int(input())
    S = list(input())
    Q = int(input())
    bit = BIT(N)
    for i in range(N):
        bit.change(i+1," ",S[i])

    for _ in range(Q):
        q,a,b = input().split()
        if q == "1":
            x = S[int(a)-1]
            S[int(a)-1] = b
            bit.change(int(a),x,b)
        else:
            a = int(a)
            b = int(b)
            count = bit.sum(b) - bit.sum(a-1)
            ans = 0
            for v in count.values():
                if v > 0:
                    ans += 1
            print(ans)
main()
