#include <bits/stdc++.h>

using namespace std;
int main()
{
    int n, t;
    cin >> n;
    bool b  = false;
    for(int i = 0 ; i < n; ++i){
        cin >> t;
        if(!t)
            b = 1;
    }
    if(b)
        cout << "YES";
    else
        cout << "NO";

    return 0;
}