package yuki_coder;

import java.util.Scanner;

public class No_279 {
public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	String S = sc.nextLine();
	sc.close();
	String[] str = new String[S.length()];
	int t = 0;
	int r = 0;
	int e = 0;
	int tree = 0;
	for(int i = 1; i <=S.length(); i++){
		str[i-1] = S.substring(i-1, i);
	}
	for(int i = 0; i < S.length(); i++){
		if(str[i].equals("t")){
			t++;
		}
		if(str[i].equals("r")){
			r++;
		}
		if(str[i].equals("e")){
			e++;
		}
	}
	if(t==r&&t==e/2){
		tree = t;
	}
	System.out.println(tree);
}
}