#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <stack>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;

int main(){
  string S;
  cin >> S;

  map<char,int> memo;
  rep(i,S.length()){
    memo[S[i]]++;
  }

  int ret = 0;
  while(true){
    if(memo['t']>0 && memo['r']>0 && memo['e']>1){
      ret++;
      memo['t']--;
      memo['r']--;
      memo['e']-=2;
    }else{
      break;
    }
  }

  cout << ret << endl;

  return 0;
}