import java.io.*;
import java.util.*;

public class Exercise64{
  public static void main (String[] args) throws IOException{

    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    String num = new String(in.readLine());
    int n = Integer.parseInt(num);

    String[][] greetings = new String[n][n];

    for(int i = 0; i < n; i++){
      String str = new String(in.readLine());
      String[] strArray = str.split(" ");
      greetings[i] = strArray;
    }

    LinkedList<Integer> answer = new LinkedList<Integer>();
    for(int a = 0; a < n; a++){
      boolean flag = true;
      for(int b = 0; b < n; b++){
        if (!greetings[b][a].equals("nyanpass") && !greetings[b][a].equals("-")){
          flag = false;
        }
      }
      if (flag){
        answer.add(a + 1);
      }
    }
    if (answer.size() == 1){
      System.out.println(answer.get(0));
    }else{
      System.out.println(-1);
    }
  }
}