#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <cstring>
#include <cctype>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <set>
#include <map>
#include <list>
#include <stdio.h>
#include <string.h>
#include <cstdlib>
#include <math.h>
#include <bitset>
#include <iterator>
#include <iomanip>
#include <sstream>
#define INF 2000000000
using namespace std;
int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
#define sym cout<<"---------"<<endl;
#define ll long long
#define PL pair<long long, long long>
#define P pair<int,int>
#define mk make_pair
#define en endl
#define WHITE 0
#define BLACK 2
#define GRAY 1
#define RE return 0
#define int ll

bool areyou[105];

signed main(){
  int n;
  cin>>n;
  for(int i=0; i<=n; i++) areyou[i]=true;
  for(int i=1; i<=n; i++){
    for(int j=1; j<=n; j++){
      string ch;
      cin>>ch;
      if(i==j) continue;
      if(ch!="nyanpass") areyou[j]=false;
    }
  }
  int ans=0;
  for(int i=1; i<=n; i++){
    if(areyou[i]){
      if(ans){
        cout<<-1<<en;
        RE;
      }else ans=i;
    }
  }
  if(ans) cout<<ans<<en;
  else cout<<-1<<en;
}