#include<cstdio>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<string>
#include<algorithm>
#include<iostream>
#define ll long long 
using namespace std;
const int maxn = 110;
const int inf = 0x3f3f3f3f;
int  n, m, k, N, t;
int main()
{
	scanf("%d", &n);
	int flag = 0;
	while (n--) 
	{
		scanf("%d", &k);
		if (k == 1)
			flag = 1;
	}
	if (flag)printf("YES\n");
	else
		printf("NO\n");

}