#include<stdio.h>

int main() {
	char str[1000001];
	char flg[26];
	int ans = 0;

	for (int i = 0; i < 26; i++)
		flg[i] = 0;

	scanf("%s", str);
	
	for (int i = 0; str[i] != '\0'; i++)
		flg[str[i] - 'a']++;

	if (flg['t' - 'a'] > flg['r' - 'a']) {
		ans = flg['r' - 'a'];
	}
	else {
		ans = flg['t' - 'a'];
	}
	if (flg['e' - 'a'] / 2 > flg['r' - 'a']) {
		ans = flg['r' - 'a'];
	}
	else {
		ans = flg['e' - 'a'] / 2;
	}

	printf("%d", ans);

	return 0;
}