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

class Program
{
    static void Main(string[] args)
    {
        string s = Console.ReadLine();
        int[] tree = new int[3];

        for (int i = 0; i < s.Length; i++)
        {
            switch (s[i].ToString())
            {
                case "t":
                    tree[0]++;
                    break;
                case "r":
                    tree[1]++;
                    break;
                case "e":
                    tree[2]++;
                    break;
            }
        }

        tree[2] /= 2;

        Console.WriteLine(tree.Min());
    }
}