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

int main() {

string s;
cin>>s;
int n=0;
map<char,int> m;
	for (int i = 0; i < s.length(); ++i) {
			m[s[i]]++;
	}
	n=min(m['t'],m['r']);
	cout<<min(n,m['e']/2)<<endl;
}