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})

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

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