6. The following is an algorithm for fast modular exponentiation:

(b) If there is a ?-bit exponent ? with \[ \left\lceil \frac{k}{2} \right\rceil \] bits of “1”, where ⌈ ⌉ denotes a
ceiling function. How many times of multiplications in this algorithm to
calculate b^e mod m. Please explain your answer. (10%)