#include <bits/stdc++.h>
using namespace std;

int main(){
  string S;
  cin>>S;
  map<char,int>mp;
  int len=S.length();
  for(int i=0;i<len;i++){
    mp[S.at(i)]++;
  }
  cout<<min(min(mp['t'],mp['r']),mp['e']/2)<<endl;
  return 0;
}