import java.util.Scanner;

class Main {
	public static void main(String[] args) throws Exception {
		Scanner in = new Scanner(System.in);
		String s = in.nextLine();
		in.close();

		String str;
		int t = 0;
		int r = 0;
		int e = 0;
		int tree = 0;
		int memory = 0;
		for(int i=1; i<=s.length(); i++) {
			str = s.substring(i-1,i);
			if(str.equals("t")) t++;
			if(str.equals("r")) r++;
			if(str.equals("e")) e++;
		}

		memory = t;
		if(memory > r) memory = r;
		if(memory > e/2) memory = e/2;
		tree = memory;

		System.out.println(tree);
	}
}