# C - Distinct or Not
# https://atcoder.jp/contests/abc154/tasks/abc154_c

num = int(input())
p = list(map(int, input().split()))
list.sort(p)

ret = "YES"
for i in range(num-1):
    if p[i] == p[i+1]:
        ret = "NO"
        break

print("{}".format(ret)) num = int(input()) num int(input()) int input() input p = list(map(int, input().split())) p list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split list.sort(p) list.sort list sort p ret = "YES" ret "YES" for i in range(num-1):
    if p[i] == p[i+1]:
        ret = "NO"
        break i range(num-1) range num-1 num 1 if p[i] == p[i+1]:
        ret = "NO"
        break p[i] == p[i+1] p[i] p i p[i+1] p i+1 i 1 ret = "NO" ret "NO" break print("{}".format(ret)) print "{}".format(ret) "{}".format "{}" format ret ret = "NO" "NO" ret ret = "YES" "YES" ret p = list(map(int, input().split())) list(map(int, input().split())) p num = int(input()) int(input()) num
# C - Distinct or Not
# https://atcoder.jp/contests/abc154/tasks/abc154_c

num = int(input())
p = list(map(int, input().split()))
list.sort(p)

ret = "YES"
for i in range(num-1):
    if p[i] == p[i+1]:
        ret = "NO"
        break

print("{}".format(ret))