#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;
using ll = long long;

int main() {
    int N;
    cin >> N;
    vector<vector<string>> v(N, vector<string>(N));
    for(int i=0; i<N; ++i) {
        for(int j=0; j<N; ++j) {
            cin >> v[i][j];
        }
        v[i][i] = "nyanpass";
    }
    int res = -1;
    for(int i=0; i<N; ++i) {
        bool ok = true;
        for(int j=0; j<N; ++j) {
            ok &= v[j][i] == "nyanpass";
        }
        if(ok) {
            if(res != -1) {
                res = -1;
                break;
            } else {
                res = i+1;
            }
        }
    }
    cout << res << endl;
}