#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <cmath>
#include <cstdlib>
#include <sstream>
#include <regex>
#include <cstdio>
#include <iterator>

#define N 1000
#define re(i,n) for(int i=0;i<(n);i++)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define fe(i,n,f) for_each(i,n,f)
using namespace std;

typedef long long ll;

int main(void){
	string s;
	std::map<char,int> m;
	cin>>s;
	re(i,s.size())m[s[i]]++;
	int k=min(m['t'],m['r']);
	k=min(k,m['e']/2);
	cout<<k<<endl;
	
	return 0;
}