import java.util.*;

public class Run {
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        int ans = -1;

        int N = scan.nextInt();
        String A;
        boolean b [] = new boolean[N];
        int flag = 0;

        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++) {
                A = scan.next();
                if (i==j) continue;
                if (!b[j]) {
                    if (!A.equals("nyanpass")) {
                        b[j] = true;
                    }
                }
            }
        }

        for (int i = 0; i < N; i++) {
            if (!b[i]) {
                if (flag!=0) break;
                flag = i+1;
            }
            if (i==N-1 && flag!=0) ans = flag;
        }

       System.out.println(ans);
    }
}