#include<bits/stdc++.h>
#define rep(i,a,n) for (int i = a;i < n;i++)
#define per(i,n,a) for (int i = n-1;i >= a;i--)
using namespace std;

int main() {
    int n;
    cin >> n;
    string s[100][100];
    rep(i,0,n){
        rep(j,0,n){
            cin >> s[i][j];
        }
    }
    set<int> st;
    rep(i,0,n){
        int cnt{0};
        rep(j,0,n){
            if(s[j][i] == "nyanpss"){
                cnt++;
            }
        }
        if(cnt == n - 1){
            st.insert(i);
        }
    }
    cout << (st.size() == 1 ? *begin(st) + 1 : -1) << endl;
}