#include<iostream>
#include<cstdio>
#include<string>
using namespace std;

int main() {
	string str;
	int n[123] = {};

	cin >> str;
	for (auto i = str.begin(); i != str.end(); i++)
	{
		n[*i]++;
	}

	int ans = 10000000;
	if (ans > n['t']) ans = n['t'];
	if (ans > n['r']) ans = n['r'];
	if (ans > (n['e'] / 2)) ans = n['e'] / 2;
	cout << ans << endl;

	return 0;
}