#include<bits/stdc++.h>
#define REP(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
typedef long long int ll;
int main()
{
  string S;
  map<char,int> mp;
  cin >> S;
  REP(i,S.size()){
    mp[S[i]]++;
  }
  cout << min(min(mp['t'],mp['r']),mp['e']/2) << endl;  
  return 0;
}