def main():
    N = int(input())
    A = input().split()
    if len(set(A)) == N:
        print("YES")
    else:
        print("NO")


if __name__ == '__main__':
    main() def main():
    N = int(input())
    A = input().split()
    if len(set(A)) == N:
        print("YES")
    else:
        print("NO") main N = int(input()) N int(input()) int input() input A = input().split() A input().split() ().split () input split if len(set(A)) == N:
        print("YES")
    else:
        print("NO") len(set(A)) == N len(set(A)) len set(A) set A N print("YES") print "YES" print("NO") print "NO" if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    N = int(input())
    A = input().split()
    if len(set(A)) == N:
        print("YES")
    else:
        print("NO") def main():
    N = int(input())
    A = input().split()
    if len(set(A)) == N:
        print("YES")
    else:
        print("NO") main
def main():
    N = int(input())
    A = input().split()
    if len(set(A)) == N:
        print("YES")
    else:
        print("NO")


if __name__ == '__main__':
    main()
