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

class Ideone{
    public static void main(String[] args) throws Exception{
        // your code goes here
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        int[] ans = new int[n];
        
        for(int i=0;i<n;i++){
            String[] lines = br.readLine().split(" ");
            for(int j=0;j<n;j++){
                if(i!=j){
                    String word = lines[j];
                    if(!word.equals("nyanpass")){
                        ans[j]++;
                    }
                }
            }
        }
        
        int answer = -1;
        for(int i=0;i<n;i++){
            if(ans[i] == 0){
                if(answer != -1){
                    answer = -1;
                    break;
                }
                answer = i+1;
            }
        }
        
        System.out.println(answer);
    }
}