n = int(input())
greeting = []
guess = []
ans = []
for i in range(n):
  greeting.append(list(input().split()))

for i in range(n):
  guess.append([])
  for j in range(n):
    guess[i].append(greeting[j][i])

for i in range(n):
  if guess[i].count('nyanpass') == n-1:
    ans.append(i + 1)

if len(ans) >= 2 or len(ans) == 0:
  print(-1)
else:
  print(ans[0])