#include <iostream>
using namespace std;

int main ()
{
    int n;
    cin>>n;
    int dem_0 = 0;
    int dem_1 = 0;
    int tmp;
    for (int i=1; i<=n; i++)
    {
        cin>>tmp;
        if (tmp==0)
            dem_0++;
        else
            dem_1++;
    }
    if (dem_0==1)
        cout<<"YES";
    else
        cout<<"NO";
    return 0;
}