#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<queue>
#include<cmath>
#include<string>
using namespace std;
typedef long long LL;
typedef unsigned long long ull;
const int inf = 0x3f3f3f3f;
const LL infll = 0x3f3f3f3f3f3f3f3f;
const LL mod = 1e9 + 7;
const double eps = 1e-8;
const double pi = acos(-1.0);
const int maxn = 1e5 + 5;
const int maxm = 1.5e7 + 5;
using namespace std;
int main()
{
	int n;
	int flag = 0;
	cin >> n;
	while (n--)
	{
		int t;
		cin >> t;
		if (t == 1) flag = 1;
	}
	if (flag)cout << "YES" << endl;
	else cout << "NO" << endl;
	return 0;
}