# -*- coding: utf-8 -*-

S = raw_input()
tree = [0] * 3

for i in S:
    if i == 't':
        tree[0] += 1
    elif i == 'e':
         tree[1] += 1
    elif i == 'r':
        tree[2] += 1

tree[1] /= 2
print min(tree)