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


namespace YukiCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var va = Console.ReadLine().Where(c => c == 't' || c == 'r' || c == 'e');
            var nt = va.Count(c => c == 't');
            var nr = va.Count(c => c == 'r');
            var ne = va.Count(c => c == 'e') / 2;
            var na = nt < nr ? nt : nr;
            var nb = na < ne ? na : ne;
            Console.WriteLine(nb);
            Console.ReadLine();
        }
    }
}