import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

import static java.lang.System.in;


public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        int N = Integer.parseInt(reader.readLine());
        String[] inputs;
        int[][] table = new int[N][N];
        for (int i = 0; i < N; i++) {
            inputs = reader.readLine().split(" ");
            for (int j = 0; j < N; j++) {
                if (inputs[j].equals("nyanpass")) {
                    table[i][j] += 1;
                }
            }
        }

        int[] villagers = new int[N];
        for (int i = 0; i < N; i++) {
            int counter = 0;
            for (int j = 0; j < N; j++) {
                if (table[j][i] == 1) {
                    counter += 1;
                }
            }
            villagers[i] = counter;
        }


        int possibleNum = 0;
        int villagerId = -1;
        for (int i = 0; i < N; i++) {
            if (villagers[i] == N - 1) {
                possibleNum += 1;
                villagerId = i+1;
            }
        }
        if(possibleNum==1){
            System.out.println(villagerId);
        } else {
            System.out.println(-1);
        }

    }
}