#include <bits/stdc++.h>

using namespace std;

int main()
{
    string s;
    cin>>s;
    int ar[26];
    memset(ar,0,sizeof(ar));
    for(int ctr1=0;ctr1<s.size();ctr1++)
        ar[s[ctr1]-'a']++;
    cout<<min(min(ar['t'-'a'],ar['r'-'a']),ar['e'-'a']/2)<<endl;
    return 0;
}