#include <stdio.h>

int main() {
	char c;
	int t = 0, r = 0, e = 0, tree;

	while ((c = getchar()) != '\n') {
		if (c == 't') t++;
		else if (c == 'r') r++;
		else if (c == 'e') e++;
	}

	tree = t;
	if (r < tree) tree = r;
	if (e / 2 < tree) tree = e / 2;

	printf("%d\n", tree);
	return 0;
}