#coding: UTF-8

import sys
import re
import itertools
from collections import deque

### defs ###


### main ###
N = int(sys.stdin.readline())
A = []
for n in range(N):
	A.append(sys.stdin.readline().split())

for i in range(N):
	for j in range(i+1,N):
		A[i][j], A[j][i] = A[j][i], A[i][j]
ans=-1
cnt=0
for n in range(N):
	if(A[n].count("nyanpass")==N-1):
		cnt+=1
		ans=n+1

if(cnt!=1):
	ans=-1
print(ans)