#include<iostream>
#include<stdio.h>
#include<map>

using namespace std;

int main(){

    string str;
    cin>> str;

    map<char, int> mp;
    for(int i=0; i<str.size(); i++){
        mp[str[i]]++;
    }

    cout<< min(mp['e']/2, min(mp['t'], mp['r']))<< endl;

    return 0;
}