package yukicorder;

import java.util.Scanner;

public class No239 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		String[][] murabito = new String[n][n];
		int count = 0;
		int ans = -1;

		for(int i = 0; i < n; i++){
			for(int j = 0; j < n; j++){
				murabito[i][j] = sc.next();
			}
		}

		for(int i = 0; i < n; i++){
			for(int j = 0; j < n; j++){
				if(i==j||murabito[j][i].equals("nyanpass")){
					if(j==n-1){
						ans=i+1;
						count++;
					}
					continue;
				}else{
					break;
				}
			}
		}
		if(count > 1){
			ans = -1;
		}
		System.out.println(ans);

	}
}