#include <bits/stdc++.h>
using namespace std;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))

bool p[111];

int main(){
    int n;
    cin >> n;
    REP(i,n)REP(j,n){
        string s; cin >> s;
        if(i==j) continue;
        if(s != "nyanpass") p[j] = true;
    }
    int cnt = 0, res;
    REP(j,n){
        if(!p[j]){
            cnt++;
            res = j + 1;
        }
    }
    if(cnt != 1) res = -1;
    cout << res << endl;
}