S = input()

d = dict(t=0, r=0, e=0)

for c in S:
    if c == "t":
        d["t"] += 1
    elif c == "r":
        d["r"] += 1
    elif c == "e":
        d["e"] += 1

print(min(d["t"], d["r"], d["e"] // 2))