#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	
	string s;
	cin>>s;
	
	int ind = -1;
	
	rep(i,s.size()){
		if(s.substr(i,4)=="pain"){
			ind = i;
			break;
		}
	}
	
	if(ind==-1){
		cout<<-1<<endl;
	}
	else{
		int ans = 0;
		rep(i,ind){
			if(s.substr(i,3)=="pon")ans++;
		}
		if(ans < 2)ans = -1;
		else ans -= 1;
		cout<<ans<<endl;
	}
	
	return 0;
}