# -*- coding: utf-8 -*-
greeting = "nyanpass"

n = int(input())
result = -1
a = []
for i in range(n):
    a.append([j == greeting for j in input().split()])

rentyon = []
for i in range(n):
    lst = [j for j in range(n)]
    lst.pop(i)
    if [a[k][i] for k in lst].count(False) == 0:
        rentyon.append(i + 1)

result = -1
if len(rentyon) == 1:
    result = rentyon[0]
print(result)