#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;

int main(){
    int t = 0, r = 0, e = 0;
    string s;
    cin >> s;
    for (int i = 0; i < s.size(); i++){
        if (s[i] == 'e') e++;
        else if (s[i] == 'r') r++;
        else if (s[i] == 't') t++;
    }
    cout << min({e/2, r, t}) << endl;
}