def main():
    N = int(input())
    A = [ int(a) for a in input().split()]
    A_ = set(A)
    if len(A)==len(A_):
        print("YES")
    else:
        print("NO")
if __name__ == "__main__":
    main() def main():
    N = int(input())
    A = [ int(a) for a in input().split()]
    A_ = set(A)
    if len(A)==len(A_):
        print("YES")
    else:
        print("NO") main N = int(input()) N int(input()) int input() input int(a) for a in input().split() for a in input().split() a input().split() ().split () input split for a in input().split() int(a) int a A = [ int(a) for a in input().split()] A [ int(a) for a in input().split()] A_ = set(A) A_ set(A) set A if len(A)==len(A_):
        print("YES")
    else:
        print("NO") len(A)==len(A_) len(A) len A len(A_) len A_ print("YES") print "YES" print("NO") print "NO" if __name__ == "__main__":
    main() __name__ == "__main__" __name__ "__main__" main() main def main():
    N = int(input())
    A = [ int(a) for a in input().split()]
    A_ = set(A)
    if len(A)==len(A_):
        print("YES")
    else:
        print("NO") def main():
    N = int(input())
    A = [ int(a) for a in input().split()]
    A_ = set(A)
    if len(A)==len(A_):
        print("YES")
    else:
        print("NO") main
def main():
    N = int(input())
    A = [ int(a) for a in input().split()]
    A_ = set(A)
    if len(A)==len(A_):
        print("YES")
    else:
        print("NO")
if __name__ == "__main__":
    main()