left and right to 1 and n respectively.left is less than or equal to right:
a. Calculate the middle of the current range as mid = left + (right - left) / 2.
b. Make a guess using mid and store the result of guess(mid).
c. If the result is 0, return mid as the picked number.
d. If the result is -1, adjust the right pointer to mid - 1.
e. If the result is 1, adjust the left pointer to mid + 1.