#include <iostream>
using namespace std;
int al[26];
int main(){
    string s;cin>>s;
    for(int i = 0; s.size() > i; i++){
        al[s[i]-'a']++;
    }
    cout << min(min(al['t'-'a'],al['r'-'a']),al['e'-'a']/2) << endl;
}