s = input()
s.replace("_", "")
s += "_____"
i = 0
cnt = 0
while i < len(s):
    if s[i : i + 3] == "pon":
        cnt += 1
        i += 3
    elif s[i : i + 4] == "pain":
        if cnt < 2:
            print(-1)
            exit()
        else:
            print(cnt - 1)
            exit()
    elif s[i] == "_":
        print(-1)
        exit()
    else:
        i += 1