#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n;
    cin >> n;

    string a[n][n];
    int f[n][n];
    rep(i,n)rep(j,n){
        cin >> a[i][j];
        if(a[i][j] == "nyanpass")f[i][j] = 1;
        else f[i][j] = 0;
    }

    int ans = -1;

    rep(j,n){
        int cnt = 0;
        rep(i,n)cnt += f[i][j];
        if(cnt == n){
            if(ans != -1){
                cout << -1 << endl;
                return 0;
            }
            ans = j + 1;
        }
    }
    cout << ans << endl;
    return 0;
}