# -*- coding: utf-8 -*-

N = int(input())
A = []
for i in range(N):
    a = list(input().split())
    A.append(a)

ren = []
for j in range(N):
    is_ren = True
    for i in range(N):
        if A[i][j] != 'nyanpass' and i != j:
            is_ren = False
            break
    if is_ren:
        ren.append(j+1)

if len(ren) == 1:
    print(ren[0])
else:
    print(-1)