import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean[][] probables = new boolean[n][n];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                probables[i][j] = (sc.next().equals("nyanpass"));
            }
        }
        ArrayList<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            boolean flag = true;
            for (int j = 0; j < n; j++) {
                if (i == j) {
                    continue;
                }
                flag &= probables[j][i];
            }
            if (flag) {
                list.add(i + 1);
            }
        }
        if (list.size() == 1) {
            System.out.println(list.get(0));
        } else {
            System.out.println(-1);
        }
    }
}