using System;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        int treeCount = 0;
        var line = Console.ReadLine().ToCharArray().OrderBy(x => x == 't').ThenBy(x => x == 'r').ThenBy(x => x == 'e').ToArray();
        Array.Reverse(line);
        int tCnt = line.Count(x => x == 't');
        int rCnt = line.Count(x => x == 'r');
        int eCnt = line.Count(x => x == 'e');

        if ( tCnt == 0 || 
             rCnt == 0 ||
             eCnt < 2)
        {
            Console.WriteLine(treeCount);
            return;
        }

        int treeCnt = 0;
        while (tCnt >= 1 && rCnt >= 1 && eCnt >= 2)
        {
            treeCnt++;
            tCnt--;
            rCnt--;
            eCnt -= 2;
        }
        Console.WriteLine(treeCnt);
    }
}