def solve(s):
    if len(s) < 6:
        return -1
    cnt = 0
    for i in range(len(s) - 3):
        if s[i:i+3] == "pon":
            cnt += 1
        elif s[i:i+4] == "pain":
            if cnt >= 2:
                return cnt - 1
            else:
                return -1
    return -1

S = input()
print(solve(S))