n = int(input())
la = [True]*n
for i in range(n):
	ls = input().split()
	for j in range(n):
		if la[j] and ls[j] != "-" and ls[j] != "nyanpass":
			la[j] = False
if True in la:
	if la.count(True) == 1:
		print(la.index(True)+1)
	else:
		print(-1)
else:
	print(-1)