//https://ncode.syosetu.com/n4830bu/279/
#include <bits/stdc++.h>
using namespace std;

int main() {
    string S;
    cin >> S;
    vector<int> cnt(26);
    for (auto&& c : S) {
        cnt[c - 'a']++;
    }
    cout << min({cnt['t' - 'a'], cnt['r' - 'a'], cnt['e' - 'a'] / 2}) << endl;
}