#include <iostream>
#include <vector>
#include <algorithm>
#include <string>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)

using namespace std;

typedef long long int lli;

int main() {
    string s;
    cin >> s;
    int cnt[128] = {};
    for (char &c: s) {
        cnt[c]++;
    }
    cout << min({cnt['t'], cnt['r'], cnt['e'] / 2}) << endl;
    return 0;
}