#include<iostream>
#include<string>

int main() {
	int alpha[26] = { 0 };
	std::string str;
	std::cin >> str;

	for (int i = 0; i < str.length(); i++) {
		alpha[str[i] - 'a']++;
	}

	int treecount = 0;
	while (true) {
		if (alpha['t' - 'a'] <= 0) break;
		alpha['t' - 'a']--;
		if (alpha['r' - 'a'] <= 0) break;
		alpha['r' - 'a']--;
		if (alpha['e' - 'a'] <= 1) break;
		alpha['e' - 'a'] -= 2;
		treecount++;
	}

	std::cout << treecount << std::endl;
	return 0;
}