def partition(a, left, right):
    pivot = a[right]
    i = left - 1
    for j in range(left, right):
        if _______________:
            i += 1
            a[i], a[j] = a[j], a[i]
    a[i + 1], a[right] = a[right], a[i + 1]
    return i + 1