#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <algorithm>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <climits>
#include <cstdio>
#define REP(i, n) for(int i = 0;i < n;i++)
#define FOR(i,m,n) for(int i = m; i < n; i++)
#define FOREACH(i, n) for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(v) ((int)v.size())
#define INF INT_MAX/2

#define pb push_back
#define mp make_pair

using namespace std;
typedef long long llong;

const int dx[6] = {1, -1, 1, 0, -1, 0};
const int dy[6] = {1, -1, 0, 1, 0, -1};

inline bool valid(int x, int w){return 0 < x && x <= w;}

map<char, int> tree;

int main(){
	string str;
	cin >> str;
	
	REP(i, str.size()) tree[str[i]]++;
	
	tree['e']/=2;
	
	int mini=tree['t'];
	mini=min(mini, tree['r']);
	mini=min(mini, tree['e']);
	
	cout << mini << endl;
}