def bisect_right(a, x):
    left, right = 0, len(a)
    # [left; right)
    while right - left > 1: # until [left, right) == {x}
        assert (x not in a) or (x in a[left:right])
        mid = (left + right) // 2
        print(mid)
        if a[mid] <= x:
            left = mid
        else:
            right = mid
    if a[left] == x: # why not m?
        return left
    else:
        return None

def bisect_left(a, x):
    left, right = -1, len(a) - 1
    # (left; right]
    while right - left > 1: # until (left, right] == {x}
        #assert (x not in a) or (x in a[left+1:right+1]) # x in (left; right]
        mid = (left + right) // 2
        print(mid)
        if a[mid] < x:
            left = mid
        else:
            right = mid
    print(right)
    if a[right] == x: # why not m?
        return right
    else:
        return None

a = [3, 4, 5, 6, 8, 7, 9, 10]
print(bisect_left(a, 8))
#a = [1, 3, 4, 4, 4, 5, 6, 6]
#print(bisect_right(a, 4))