#include <bits/stdc++.h>
using namespace std;

#define repu(i, a, b) for (int i = (a); i < (b); ++i)
#define repd(i, a, b) for (int i = (a); i > (b); --i)
#define mem(a, x) memset(a, x, sizeof(a))
#define all(a) a.begin(), a.end()
#define uni(a) a.erase(unique(all(a)), a.end())

typedef long long ll;
const int MOD = 1000000007;

template<class T, class U> inline T tmin(T a, U b) {return (a < b) ? a : b;}
template<class T, class U> inline T tmax(T a, U b) {return (a > b) ? a : b;}
template<class T, class U> inline void amax(T &a, U b) {if (b > a) a = b;}
template<class T, class U> inline void amin(T &a, U b) {if (b < a) a = b;}
template<class T> inline T tabs(T a) {return (a > 0) ? a : -a;}
template<class T> T gcd(T a, T b) {while (b != 0) {T c = a; a = b; b = c % b;} return a;}

int main(int argc, char *argv[]) {
	ios_base::sync_with_stdio(false);
	
	string s;
	vector<int> cnt(150, 0);
	cin >> s;
	repu(i, 0, s.size()) cnt[s[i]]++;
	
	int ret = min(cnt['t'], cnt['r']);
	amin(ret, cnt['e'] / 2);
	
	cout << ret << endl;
	
	return 0;
}