import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int ansN = 0;
    int ans = 0;
    String[][] a = new String[N][N];
    for(int i = 0; i < N; i++) {
      for(int j = 0; j < N; j++) {
        a[i][j] = sc.next();
      }
    }
    for(int j = 0; j < N; j++) {
      boolean flg = true;
      for(int i = 0; i < N; i++) {
        if((i != j) && (!(a[i][j].equals("nyanpass")))) flg = false;
      }
      if(flg) {
        ansN++;
        ans = j + 1;
      }
    }
    if(ansN == 0 || ansN > 1) ans = -1;
    System.out.println(ans);
  }
}