s=input()
flag=True
ans=0
n=len(s)
for i in range(n-3):
  if flag:
    if s[i:i+3]=='pon':
      ans+=1
    if s[i:i+4]=='pain':
      flag=False
if flag==False and ans>=2:
  print(ans-1)
else:
  print(-1)