from lib import str_to_ints


def part_1(data):
    layer_to_depth = {}
    for line in data.splitlines():
        a, b = str_to_ints(line)
        layer_to_depth[a] = b

    layer_to_pos = {l: 0 for l in layer_to_depth.keys()}
    layer_to_dir = {l: -1 for l in layer_to_depth.keys()}
    target = max(list(layer_to_depth.keys()))

    r = 0
    layer = 0
    while layer <= target:
        if layer in layer_to_pos and layer_to_pos[layer] == 0:
            r += (layer * layer_to_depth[layer])

        for k in layer_to_pos.keys():
            if layer_to_pos[k] == 0 or (layer_to_pos[k] + 1) == layer_to_depth[k]:
                layer_to_dir[k] *= -1
            layer_to_pos[k] += layer_to_dir[k]
        layer += 1
    print(r)


def part_2(data):
    eqs = []
    for line in data.splitlines():
        layer, depth = str_to_ints(line)
        period = (depth - 1) * 2
        eqs.append((layer, period))
        
    for delay in range(1, 1_000_000_000):
        for layer, period in eqs:
            if (delay + layer) % period == 0:
                break
        else:
            print(delay)
            return



def main():
    data = open(0).read().strip()
    part_1(data)
    part_2(data)


if __name__ == "__main__":
    main()