#include <bits/stdc++.h>
#define PB push_back
#define MP make_pair
#define REP(i,n) for (int i=0;i<(n);i++)
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define ALL(a) (a).begin(),(a).end()
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
const int INF=1e9;
const int MOD=100000;
int B=1000000;
int main(){
      bool f[100];
      memset(f,true,sizeof(f));
      int n;
      cin>>n;
      string s;
      REP(i,n)REP(j,n){
            cin>>s;
            if(i==j)continue;
            if(s!="nyanpass"){
                  f[j]=false;
            }
      }
      vector<int> ans;
      REP(i,n)if(f[i])ans.PB(i);
      if(ans.size()==1)cout<<ans[0]+1<<endl;
      else cout<<-1<<endl;
}