最左边那个 17 在哪

数组是 [13, 15, 17, 17, 17, 23, 24]。运行下面这段程序：

def left_bound(a, target):
    lo = 0
    hi = len(a) - 1
    got = -1
    while lo <= hi:
        mid = (lo + hi) // 2
        if a[mid] == target:
            got = mid
            hi = mid - 1
        elif a[mid] < target:
            lo = mid + 1
        else:
            hi = mid - 1
    return got

print(left_bound([13, 15, 17, 17, 17, 23, 24], 17))