def smaller(x, y):
	if x < y:
		return x
	else:
		return y

s = raw_input()
t = 0
r = 0
e = 0

for i in range(0, len(s)):
	if s[i] == 't':
		t += 1
	elif s[i] == 'r':
		r += 1
	elif s[i] == 'e':
		e += 1

print smaller(smaller(t, r), e/2)