#include <bits/stdc++.h>

using namespace std;

int main(void) {
  string s;
  cin >> s;

  map<char, int> mp;
  for (int i = 0; i < s.size(); i++) {
    mp[s[i]]++;
  }

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

  return 0;
}