#include<iostream>
#include<string>
using namespace std;

string s;
int num[256];

int main(){
	cin >> s;
	for( int i = 0; i < s.length(); i++ )
		num[s[i]]++;
	
	char tree[6] = "tree";
	int ans = 1145140;
	for( int i = 0; i < 4; i++ )
		ans = min(ans, num[tree[i]]);
	
	cout << ans << endl;
	return 0;
}