#include<iostream>
#include<string>
#include<vector>

#define rep(i,n) for(i=0; i<n; i++)

using namespace std;

int main()
{
    int n;
    cin >> n;
    
    int i,j;
    int renchon[100]={0};
    string s;
    rep(i,n) {
        rep(j,n) {
            cin >> s;
            if(s=="nyanpass") {
                renchon[j+1]++;
            }
        }
    }
    int cnt=0,specific=0;
    for(i=0;i<100;i++){
        if(renchon[i]==n-1){ cnt++; specific=i; }
    }
    if(cnt!=1) { cout << -1 << endl; }
    else if(specific!=0) { cout << specific << endl; }
    else { cout << -1 << endl; }
    return 0;
}