#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef int ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<ut,pr> ppr;
typedef vector<ppr> Vppr;
typedef priority_queue<pr,Vpr,greater<pr> > PQ;
typedef priority_queue<ppr,Vppr,greater<ppr> > PprQ;
const int SIZE=5+3*1e+5;
const ut INF=1<<30;
const ld eps=1e-6;
const LL p=7+1e+9;
int nums[SIZE];
int main(){
	string s;
	cin >> s;
	REP(i,s.size())
		nums[s[i]-'a']++;
	cout << min(min(nums['t'-'a'],nums['r'-'a']),nums['e'-'a']/2) << endl;
}