N = int(input())
A = []
for i in range(N):
	A.append(list(input().split()))
	
ans = []
for j in range(N):
	for i in range(N):
		if i == j:
			continue
		if A[i][j] != "nyanpass":
			break
	else:
		ans.append(j + 1)
		
if len(ans) != 1:
	print(-1)
else:
	print(ans[0])