// No.279 木の数え上げ
// https://yukicoder.me/problems/no/279
//

#include <iostream>
#include <vector>
using namespace std;

int solve(string &S);

int main() {
    string S;
    cin >> S;
    int ans = solve(S);
    cout << ans << endl;
}

int solve(string &S) {
    vector<int> letters(26);
    for (char c: S) {
        letters[c - 'a']++;
    }

    int t = letters['t' - 'a'];
    int r = letters['r' - 'a'];
    int e = letters['e' - 'a'];
    return min(min(t, r), e/2);
}