n=int(input())
a=[]
# print(a)
for i in range(n):
	a.append(list(map(str,input().split(' '))))
	# print(a[i])
ans=-1
for i in range(n):
	f=True
	for j in range(n):
		if i == j:
			continue
		if a[j][i] != "nyanpass":
			f=False
	if f:
		if ans == -1:
			ans = i
		else:
			ans = -2

if ans < 0:
	print(-1)
else:
	print(ans+1)