#!/usr/bin/env python3
import sys

def main():
    # N = int(input())
    # N, X = map(int,input().split())
    # A = list(map(int,input().split()))
    S = input()
    N = len(S)
    if N < 10:
        print(-1)
        return
    c = 0
    for i in range(N - 3):
        if S[i:(i + 3)] == "pon":
            c += 1
        if S[i:(i + 4)] == "pain":
            print(c - 1)
            return
    print(-1)
    return

if __name__ == '__main__':
    main()