/* -*- coding: utf-8 -*-
 *
 * 3218.cc:  No.3218 Night Equation - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

/* global variables */

int as[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", as + i);

  for (int i = 0; i < n; i++)
    if (as[i] > 0) { puts("Yes"); return 0; }

  puts("No");
  return 0;
}