#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <sstream>
#include <string>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <limits>
#include <complex>
#include <functional>
using namespace std;
#define rep(i,n) for (int (i)=0;(i)<(int)(n);++(i))

string s;

int count(char c) {
    int cnt = 0;
    rep(i, s.length()) {
        if (s[i] == c) cnt++;
    }
    return cnt;
}

int main() {
    cin >> s;
    cout << min(min(count('t'), count('r')), count('e')/2) << endl;
}