#!/usr/bin/python
# -*- coding: utf-8 -*-

N = int(raw_input())
arr = []
for i in range(N):
  tmp = map(str, raw_input().split())
  arr.append(tmp)

arr2 = [ [ "-" for i in range(N) ] for i in range(N) ]
for i in range(N):
	for j in range(N):
		arr2[i][j] = arr[j][i]

ans = -1
for i in range(N):
	if arr2[i].count("nyanpass") == N - 1 and ans == -1:
		ans = i + 1
	elif arr2[i].count("nyanpass") == N - 1 and ans != -1:
		print "-1"
		exit()
print ans