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

#define rep(i,n) for(int i=0;i<(n);i++)
#define pb push_back
#define all(v) (v).begin(),(v).end()

int main(){
    map<char,int>m;
    string s;
    cin>>s;
    rep(i,s.size())m[s[i]]++;

    cout<<min(min(m['t'],m['r']),m['e']/2)<<endl;
    return 0;
}