#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;

int main() {
  string s;
  cin >> s;
  int alnum['z'+1];
  memset(alnum, 0, sizeof(alnum));
  for (int i = 0; i < s.size(); i++) {
    alnum[s[i]]++;
  }
  std::cout << min(alnum['t'], min(alnum['r'], alnum['e']/2)) << std::endl;
}