using System;

public class Program {
    public static void Main() {
        string line = Console.ReadLine();
        int[] arr = new int[26];
        for (int i = 0; i < 26; i++) arr[i] = 0;
        for (int i = 0; i < line.Length; i++) arr[line[i]-'a']++;
        int ans = arr['e'-'a']/2;
        ans = Math.Min(ans, arr['r'-'a']);
        ans = Math.Min(ans, arr['t'-'a']);
        Console.WriteLine(ans);
    }
}