# [1, 3], [2, 2], [3, 1] input



def load_truck(dimensions, truck_size):
    loads = []

    for i, v in enumerate(dimensions):
        # (boxsize_count, items in box)
        tuple = (v[0], v[1])
        loads.append(tuple)

    # sort biggest boxes first (contains more items)
    value_sorted = sorted(
    loads,
    key=lambda x: x[0]
    )

    max_items = 0
    boxes_countdown = truck_size
    i = 0
    while (boxes_countdown > 0) and (i < len(value_sorted)):
        curr = value_sorted[i]
        total_boxes = curr[0]
        items_per_box = curr[1]

        if boxes_countdown >= total_boxes:
            max_items = max_items + (total_boxes * items_per_box)
            boxes_countdown = boxes_countdown - total_boxes
        else:
            max_items = max_items + (boxes_countdown * items_per_box)
            boxes_countdown = boxes_countdown - total_boxes

        i = i+1

    return max_items






def test_truck():
    tiny_truck_load = [[2, 2], [1, 3], [3, 1] ]
    tiny_truck_size = 4

    ret = load_truck(tiny_truck_load, tiny_truck_size)
    print(ret)

    assert ret == 8, "Should be 8"

if __name__ == "__main__":
    test_truck()
    print("Everything passed")