#include<bits/stdc++.h>
using namespace std;
int main(){
    int N; cin >> N;
    string nyan[N][N];
    vector<int> v;
    for(int i=0; i<N; i++){
        for(int j=0; j<N; j++){
            cin >> nyan[i][j];
        }
    }
    for(int i=0; i<N; i++){
        int nyanko = 0;
        for(int j=0 ;j<N; j++){
            if(nyan[j][i] == "nyanpass"){
                nyanko++;
            }
        }
        if(nyanko == N-1) v.push_back(i+1);
    }
    if(v.size() == 1) cout << v[0] << endl;
    else cout << -1 << endl;
    
    return 0;
}