#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#define INF 0x3f3f3f3f
#define lowbit(x) (x&(-x))
using namespace std;
typedef long long ll;

const int maxn = 1e6 + 10;

int main()
{
    int n;
    scanf("%d",&n);
    int flag = 0;
    while(n--)
    {
        int x;
        scanf("%d",&x);
        if(x == 1)
            flag = 1;
    }
    if(flag)
        puts("YES");
    else 
        puts("NO");
}