#include "iostream"
using namespace std;

int main(){
    int n,i,j;
    cin >> n;
    string greet[n][n];
    for (i = 0; i < n; i++){
        for (j = 0; j < n; j++)
            cin >> greet[i][j];
    }
    int cnt,ans;
    cnt = 0;
    ans = -1;
    for (j = 0; j < n; j++){
        for (i = 0; i < n; i++){
            if (i != j && greet[i][j] != "nyanpass")
                break;
        }
        if (i == n){
            cnt++;
            ans = j+1;
        }
        if (cnt > 1){
            ans = -1;
            break;
        }
    }
    cout << ans << endl;
    return 0;
}