N=int(input())
A=[input().split()for i in range(N)]
ans=-1
for j in range(N):
  fl=True
  for i in range(N):
    if i==j:
      continue
    if A[i][j]!="nyanpass":
      fl=False
  if fl:
    if ans==-1:
      ans=j+1
    else:
      print(-1)
      exit(0)
print(ans)