import sys
input=lambda: sys.stdin.readline().rstrip()
n=int(input())
C=[0]*n
for _ in range(n):
  A=[str(i) for i in input().split()]
  for i in range(n):
    if A[i]=="nyanpass":
      C[i]+=1
ans=0
for c in C:
  if c==n-1:
    ans+=1
if ans!=1:
  print(-1)
else:
  for i in range(n):
    if C[i]==n-1:
      print(i+1)
      break