#include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(long long)(n);++i)
#define all(a) a.begin(), a.end()
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
 
const ll MOD=1000000007;
const ll INF=1e18;
const int MAX=510000;
const double pi=acos(-1);
int dx[8] = {1,0,-1,0,1,1,-1,-1};
int dy[8] = {0,1,0,-1,-1,1,1,-1};

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false); 
  
  int n,num=0,ans;
  cin >> n;
  vector<vector<string>>vec(n,vector<string>(n));
  rep(i,n)rep(j,n)cin>>vec[i][j];
  
  rep(j,n){
    bool ok = true;
    rep(i,n){
      if(i==j)continue;
      if(vec[i][j]!="nyanpass")ok=false;
    }
    if(ok){
      num++;
      ans=j+1;
    }
  }
  if(num==1)cout << ans << endl;
  else cout << -1 << endl;
  return 0;
}