#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;

int a[105];

int main(){
    int n;
    cin >> n;
    rep(i,n) a[i] = 1;
    rep(i,n)rep(j,n){
        string s;
        cin >> s;
        if(i == j) continue;
        if(s != "nyanpass") a[j] = -1;
    }
    int ans = -1;
    bool ok = true;
    rep(i,n){
        if(a[i] == 1){
            if(ans != -1) ok = false;
            ans = i;
        }
    }

    if(ok && ans != -1) cout << ans+1 << endl;
    else cout << -1 << endl;
    return 0;
}