#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <functional>
#include <set>
#include <sstream>
#include <map>
#include <queue>
#include <stack>
using namespace std;

long long dp[110][20010];
long long mod=1000000000+7;

int main(){

	string s;
	cin>>s;
	
	int cnt[26]={};
	for(int i=0;i<s.size();i++) cnt[s[i]-'a']++;
	
	int ans=cnt['t'-'a'];
	ans=min(ans,cnt['r'-'a']);
	ans=min(ans,cnt['e'-'a']/2);
	cout<<ans<<endl;
}