import sys
input=lambda:sys.stdin.readline().rstrip()
S=input()
N=len(S)
ans=S[0:3]=='pon'
for i in range(4,N+1):
	ans+=S[i-3:i]=='pon'
	if S[i-4:i]=='pain':
		print(ans-1 if ans>1 else -1)
		sys.exit()
print(-1)