#include <bits/stdc++.h>

using namespace std;

namespace {

    typedef double real;
    typedef long long ll;

    template<class T> ostream& operator<<(ostream& os, const vector<T>& vs) {
        if (vs.empty()) return os << "[]";
        os << "[" << vs[0];
        for (int i = 1; i < vs.size(); i++) os << " " << vs[i];
        return os << "]";
    }
    template<class T> istream& operator>>(istream& is, vector<T>& vs) {
        for (auto it = vs.begin(); it != vs.end(); it++) is >> *it;
        return is;
    }

    int N;
    vector<vector<string>> F;
    void input() {
        cin >> N;
        F = vector<vector<string>>(N, vector<string>(N));
        cin >> F;
    }

    void solve() {
        vector<int> r;
        for (int j = 0; j < N; j++) {
            bool flag = true;
            for (int i = 0; i < N; i++) {
                if (i == j) continue;
                if (F[i][j] != "nyanpass") flag = false;
            }
            if (flag) {
                r.push_back(j);
            }
        }
        if (r.size() == 1) {
            cout << r[0] + 1 << endl;
        } else {
            cout << -1 << endl;
        }

    }
}

int main() {
    input(); solve();
    return 0;
}