using System;
using System.Collections.Generic;
using System.Linq;

static class Ponponpain
{
    static void Main()
    {
		var s = Console.ReadLine();
		var endIndex = s.IndexOf("pain");
		if(endIndex <= 0 )
			Console.WriteLine(-1);
		else
		{
			var pon = s.Substring(0, endIndex).Split('p').Where(x => x.StartsWith("on")).Count()-1;
			if(pon == 0)
			{
				Console.WriteLine(-1);
			} 
			else
			{
				Console.WriteLine(pon);
			}
		}
	}
}