#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < n; ++i)
typedef long long ll;
using namespace std;
const int INF = 1e9;

int main() {
    string s;
    cin >> s;

    string t = "tre";
    int cnt[3] = {0};
    rep(i, s.size()) {
        rep(j, 3) {
            if (t[j] == s[i])
                cnt[j]++;
        }
    }

    int ans = min({cnt[0], cnt[1], cnt[2] / 2});
    cout << ans << endl;

    return 0;
}