def popchr(string, char):
	if not char in string:
		return False, string 
	i = string.find(char)
	string =  string[:i] + string[(i+1):]
	return True, string

string = input()
flag = True
count = 0
while flag :
	flag, string = popchr(string, "t")
	if not flag:
		break
	flag, string = popchr(string, "r")
	if not flag:
		break
	flag, string = popchr(string, "e")
	if not flag:
		break
	flag, string = popchr(string, "e")
	if not flag:
		break
	if flag:
		count+=1
print(count)