import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int[] counts = new int[26];
        for (char c : sc.next().toCharArray()) {
            counts[c - 'a']++;
        }
        int ans = Math.min(Math.min(counts['t' - 'a'], counts['r' - 'a']), counts['e' - 'a'] / 2);
        System.out.println(ans);
    }
}