import java.util.Scanner;
import java.util.ArrayList;

class solve {
    public static void main(String args[]) {
	Scanner scan = new Scanner(System.in);

	int n = scan.nextInt();
	String a[][] = new String[n][n];
	for (int i = 0; i < n; i++) {
	    for (int j = 0; j < n; j++) {
		a[i][j] = scan.next();
	    }
	}
	ArrayList<Integer> ans = new ArrayList<Integer>();
	for (int i = 0; i < n; i++) {
	    boolean ok = true;
	    for (int j = 0; j < n; j++) {
		if (i == j) continue;
		if (!a[j][i].equals("nyanpass")) {
		    ok = false;
		    break;
		}
	    }
	    if (ok) {
		ans.add(i+1);
	    }
	}
	if (ans.size() == 1) {
	    System.out.println(ans.get(0));
	}else {
	    System.out.println("-1");
	}
    }
}