
def solve():
    if len(A) != len(set(A)):
        print("NO")
    else:
        print("YES")


if __name__ == "__main__":
    N = int(input())
    A = list(map(int, input().split()))
    solve()   def solve():
    if len(A) != len(set(A)):
        print("NO")
    else:
        print("YES") solve if len(A) != len(set(A)):
        print("NO")
    else:
        print("YES") len(A) != len(set(A)) len(A) len A len(set(A)) len set(A) set A print("NO") print "NO" print("YES") print "YES" if __name__ == "__main__":
    N = int(input())
    A = list(map(int, input().split()))
    solve()   __name__ == "__main__" __name__ "__main__" N = int(input()) N int(input()) int input() input A = list(map(int, input().split())) A list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split solve() solve N = int(input()) int(input()) N def solve():
    if len(A) != len(set(A)):
        print("NO")
    else:
        print("YES") def solve():
    if len(A) != len(set(A)):
        print("NO")
    else:
        print("YES") solve A = list(map(int, input().split())) list(map(int, input().split())) A

def solve():
    if len(A) != len(set(A)):
        print("NO")
    else:
        print("YES")


if __name__ == "__main__":
    N = int(input())
    A = list(map(int, input().split()))
    solve()  
