#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  int N;
  cin>>N;
  vector<vector<string>> S(N,vector<string>(N));
  for(int i=0;i<N;i++)for(int j=0;j<N;j++) cin>>S[i][j];
  vector<int> A={};
  for(int j=0;j<N;j++){
      bool ok = true;
      for(int i=0;i<N;i++)if(S[i][j] != "-" && S[i][j] != "nyanpass") ok = false;
      if(ok) A.push_back(j+1);
  }
  if(A.size() == 1) cout<<A[0]<<endl;
  else cout<<-1<<endl;
}