S = list(input())
c_t = 0
c_r = 0
c_e = 0
for s in S:
    if s == "t":
        c_t += 1
    if s == "r":
        c_r += 1
    if s == "e":
        c_e += 1

print(min(c_t, c_r, c_e//2))