package 練習;

import java.util.Date;
import java.util.Scanner;
public class main{
	public static void main(String[] args){
		long exec_time=new Date().getTime();
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		String[][] str=new String[n][n];

		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				str[i][j]=sc.next();
			}
		}
		int ans=-1;
		int cnt=0;
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				if(i==j||str[j][i].equals("nyanpass")){
					if(j==n-1){
						ans=i+1;
						cnt++;
					}
					continue;
				}else{
					break;
				}
			}
		}
		if(cnt>1)ans=-1;
		System.out.println(ans);
		System.err.println(new Date().getTime()-exec_time+"ms");

	}
}