def main():
    n = int(input())
    a = [int(x) for x in input().split()]
    a_s = set(a)
    if len(a) == len(a_s):
        print('YES')
    else:
        print('NO')

if __name__ == '__main__':
    main() def main():
    n = int(input())
    a = [int(x) for x in input().split()]
    a_s = set(a)
    if len(a) == len(a_s):
        print('YES')
    else:
        print('NO') main n = int(input()) n int(input()) int input() input int(x) for x in input().split() for x in input().split() x input().split() ().split () input split for x in input().split() int(x) int x a = [int(x) for x in input().split()] a [int(x) for x in input().split()] a_s = set(a) a_s set(a) set a if len(a) == len(a_s):
        print('YES')
    else:
        print('NO') len(a) == len(a_s) len(a) len a len(a_s) len a_s 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(x) for x in input().split()]
    a_s = set(a)
    if len(a) == len(a_s):
        print('YES')
    else:
        print('NO') def main():
    n = int(input())
    a = [int(x) for x in input().split()]
    a_s = set(a)
    if len(a) == len(a_s):
        print('YES')
    else:
        print('NO') main
def main():
    n = int(input())
    a = [int(x) for x in input().split()]
    a_s = set(a)
    if len(a) == len(a_s):
        print('YES')
    else:
        print('NO')

if __name__ == '__main__':
    main()