# coding=utf-8:
import collections

n = int(input())
persons = dict([(i, 0) for i in range(n)])
greeting = list()

for i in range(n):
    greeting.append(list(map(str, input().split())))

for j in range(n):
    for k in range(n):
        if greeting[j][k] == "nyanpass":
            persons[k] += 1

max_k = [k for k, v in persons.items() if v == max(persons.values())]

if len(max_k) == 1:
    if persons.get(*max_k) == n - 1:
        print(max_k[0]+1)
    else:
        print(-1)
else:
    print(-1)