import java.awt.Frame;
import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[][] table = new String[N][N];
		for(int i=0;i<N;i++){
			for(int j=0;j<N;j++){
				table[i][j]=sc.next();
			}
		}
		int ans = -1;
		t:for(int i=0;i<N;i++){
			for(int j=0;j<N;j++){
				if(i==j) continue;
				if(!table[j][i].equals("nyanpass")){
					continue t;
				}
			}
			if(ans==-1){
				ans = i+1;
			}else{
				System.out.println(-1);
				return;
			}
		}
		System.out.println(ans);
	}
}