#include <bits/stdc++.h>
using namespace std;
typedef int64_t lint;

int main()
{
    string s;
    cin>>s;
    map<char,lint> mp;
    for(lint i=0;i!=s.size();i++){
        mp[s[i]]++;
    }
    mp['e']/=2;
    cout<<min(min(mp['t'],mp['r']),mp['e'])<<endl;


    // system("pause");
}