#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <stack>
#include <vector>
#include <string>
#include <iostream>
#include <list>
#include <cstdlib>
#include <bitset>
#define lowbit(x) (x&(-x))
#define lson root<<1,l,mid
#define rson root<<1|1,mid+1,r
const long long INF = 0x3f3f3f3f3f3f3f3fLL;
const int inf = 0x3f3f3f3f;
using namespace std;
int main()
{
	int n, v;
	bool has1 = false, has2 = false;
	scanf("%d", &n);
	for (int i = 0; i < n; ++i)
	{
		scanf("%d", &v);
		if (v == 1)
			has1 = true;
	}
	if (has1)
		puts("YES");
	else
		puts("NO");
}