N = int(input())
canset = list(range(N))
for i in range(N):
	W = input().split()
	for i in canset:
		if W[i] != 'nyanpass' and W[i] != '-':
			canset.remove(i)
if len(canset) == 1:
	print(canset[0])
else:
	print(-1)