from collections import Counter

S = input()
count = Counter(S)
tree_count = dict()

for k,v in count.items():
    if k in ["t","r","e"]:
        tree_count.update({k:v})

e_num = int((tree_count["e"] if tree_count["e"] else 0)/2)

print(0 if e_num < 1 else int(min([tree_count["t"],tree_count["r"],e_num])))