S=input()

pon=0
pain=0

for i in range(len(S)):
    if S[i:i+3]=="pon":
        pon+=1
    if S[i:i+4]=="pain":
        pain=1
        break

if pon<=1 or pain==0:
    print(-1)
else:
    pon-=1
    print(pon)