def iou(boxA, boxB):

    xA = max(boxA[0], boxB[0])

    yA = max(boxA[1], boxB[1])

    xB = min(boxA[2], boxB[2])

    yB = min(boxA[3], boxB[3])

    interArea = (xB - xA + 1) * (yB - yA + 1)

    if interArea < 0:

        interArea = 0

    boxAArea = (boxA[2] - boxA[0] + 1) * (boxA[3] - boxA[1] + 1)

    boxBArea = (boxB[2] - boxB[0] + 1) * (boxB[3] - boxB[1] + 1)

    return interArea / float(boxAArea + boxBArea - interArea)