#include <iostream>
#include <fstream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

int main(void) {
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	std::cout << std::fixed;

	map<char, int> cnt;
	char c;
	while (cin >> c)
		cnt[c]++;

	cout << min(min(cnt['t'], cnt['r']), cnt['e'] / 2) << endl;
}