def main():
    import sys

    def input(): return sys.stdin.readline().rstrip()

    n, a, b = map(int, input().split())
    mod = 10 **9 + 7
    ans = pow(2, n, mod) -1
    c = 1
    for i in range(b):
        c *= n-i
        c%= mod
        c *= pow(i+1, mod-2, mod)
        c %= mod
        if i == a-1:
            ca = c
    ans -= (c+ca)%mod
    ans %= mod
    print(ans)
    





if __name__ == '__main__':
    main() def main():
    import sys

    def input(): return sys.stdin.readline().rstrip()

    n, a, b = map(int, input().split())
    mod = 10 **9 + 7
    ans = pow(2, n, mod) -1
    c = 1
    for i in range(b):
        c *= n-i
        c%= mod
        c *= pow(i+1, mod-2, mod)
        c %= mod
        if i == a-1:
            ca = c
    ans -= (c+ca)%mod
    ans %= mod
    print(ans)
     main import sys sys def input(): return sys.stdin.readline().rstrip()

     input n, a, b = map(int, input().split()) n map(int, input().split()) map int input().split() ().split () input split a b mod = 10 **9 + 7 mod 10 **9 + 7 10 **9 10 9 7 ans = pow(2, n, mod) -1 ans pow(2, n, mod) -1 pow(2, n, mod) pow 2 n mod 1 c = 1 c 1 for i in range(b):
        c *= n-i
        c%= mod
        c *= pow(i+1, mod-2, mod)
        c %= mod
        if i == a-1:
            ca = c
     i range(b) range b c *= n-i c n-i n i c%= mod c mod c *= pow(i+1, mod-2, mod) c pow(i+1, mod-2, mod) pow i+1 i 1 mod-2 mod 2 mod c %= mod c mod if i == a-1:
            ca = c
     i == a-1 i a-1 a 1 ca = c ca c ans -= (c+ca)%mod ans (c+ca)%mod c+ca c ca mod ans %= mod ans mod print(ans) print ans if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    import sys

    def input(): return sys.stdin.readline().rstrip()

    n, a, b = map(int, input().split())
    mod = 10 **9 + 7
    ans = pow(2, n, mod) -1
    c = 1
    for i in range(b):
        c *= n-i
        c%= mod
        c *= pow(i+1, mod-2, mod)
        c %= mod
        if i == a-1:
            ca = c
    ans -= (c+ca)%mod
    ans %= mod
    print(ans)
     def main():
    import sys

    def input(): return sys.stdin.readline().rstrip()

    n, a, b = map(int, input().split())
    mod = 10 **9 + 7
    ans = pow(2, n, mod) -1
    c = 1
    for i in range(b):
        c *= n-i
        c%= mod
        c *= pow(i+1, mod-2, mod)
        c %= mod
        if i == a-1:
            ca = c
    ans -= (c+ca)%mod
    ans %= mod
    print(ans)
     main
def main():
    import sys

    def input(): return sys.stdin.readline().rstrip()

    n, a, b = map(int, input().split())
    mod = 10 **9 + 7
    ans = pow(2, n, mod) -1
    c = 1
    for i in range(b):
        c *= n-i
        c%= mod
        c *= pow(i+1, mod-2, mod)
        c %= mod
        if i == a-1:
            ca = c
    ans -= (c+ca)%mod
    ans %= mod
    print(ans)
    





if __name__ == '__main__':
    main()