using System;

namespace yukicoder
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = Console.ReadLine();
            string[] t = {"t","r","e" };
            int[] a = new int[4];
            int count = 0;
            for(int i = 0; i < s.Length; i++)
            {
                string b = s.Substring(i, 1);
                for (int j = 0; j < t.Length; j++)
                {
                    if ( b== t[j])
                    {
                        a[j]++;
                    }
                }
            }
            a[2] /= 2;
           for(; ; )
            {
                a[0] -= 1;
                a[1] -= 1;
                a[2] -= 1;
                if (a[0] >= 0 && a[1] >= 0 && a[2] >= 0)
                {
                    count++;
                }
                else
                {
                    break;
                }
            }

            Console.WriteLine(count);
        }
    }
}