#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  string S;
  cin >> S;
  map<char, int> mp;
  for (char s : S) {
    mp[s]++;
  }
  int res = 1 << 28;
  res = min(res, mp['t']);
  res = min(res, mp['r']);
  res = min(res, mp['e'] / 2);
  cout << res << '\n';
  return 0;
}