using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace yukicoderTest
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = Console.ReadLine();
            int tcnt = 0;
            int rcnt = 0;
            int ecnt = 0;
            int tree = 0;
            for(int i=0;i<input.Length;i++)
            {
                string temp = input.Substring(i, 1);
                if (temp == "t")
                {
                    tcnt++;
                }
                else if (temp == "r")
                {
                    rcnt++;
                }
                else if (temp == "e")
                {
                    ecnt++;
                }
            }
            while(tcnt>=1&&rcnt>=1&&ecnt>=2)
            {
                tcnt--;
                rcnt--;
                ecnt -= 2;
                tree++;
            }
            Console.WriteLine(tree);
        }

    }
}