#include <bits/stdc++.h>
using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
typedef vector<int> vi;

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define rep(i,n) rep2(i,0,n)
#define rep2(i,m,n) for(int i=m;i<(n);i++)
#define ALL(c) (c).begin(),(c).end()

string s;
int cnt[30];
int ret;

int main() {
    cin >> s;
    rep(i, s.size()) ++cnt[s[i]-'a'];
    ret = min(cnt['t'-'a'], cnt['r'-'a']);
    ret = min(ret, cnt['e'-'a']/2);
    cout << ret << endl;
    return 0;
}