package no279;

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int[] count = new int[256];
		for(int i=0;i<s.length();i++) {
			count[s.charAt(i)]++;
		}
		int ans = count['t'];
		ans = Math.min(ans,count['r']);
		ans = Math.min(ans, count['e']/2);
		System.out.println(ans);
	}
}