#include<stdio.h>
#include<string.h>

int main(void){
  int i, j;
  int N, n = 0, num;
  char A[31];
  int S[101] = {};
  scanf("%d", &N);
  for(i = 1; i <= N; i++){
    for(j = 1; j <= N; j++){
      scanf("%s", A);
      if(i != j && strcmp(A, "nyanpass") == -1){
	S[j] = 1;
      }
    }
  }
  for(i = 0; i < N; i++){
    if(S[i] == 0){
      n++;
      num = i;
    }
  }
  if(n == 1) printf("%d\n", num);
  else printf("-1\n");
   
  return 0;
}