Codeforces Fashion in Berland

#include<bits/stdc++.h>
using namespace std;

int main()
{
    ios_base::sync_with_stdio(false);

    int n;
    while(cin >> n)
    {
        int cnt=0 , i=0;

        while(i<n)
        {
            int x;
            cin >> x;

            if(x) cnt++;

            i++;
        }

        if(n==1)
        {
            if(cnt>0) cout << "YES\n";
            else cout << "NO\n";
        }

        else
        {
            if(cnt == (n-1)) cout << "YES\n";
            else cout << "NO\n";
        }
    }

    return 0;
}