#include <iostream>
#include <algorithm>

using namespace std;

int main() {
  string s;
  cin >> s;
  int counter[256] = {0};
  for (char& c : s) {
    counter[(int)c] += 1;
  }
  int tree_count = std::min({
      counter[(int)'t'],
      counter[(int)'r'],
      counter[(int)'e'] / 2
      });
  cout << tree_count << endl;
  return 0;
}