401372: GYM100425 A Luggage Distribution

All provident tourists know about low-cost airlines. Those who used them at least once also know that their airfare usually includes neither lunch nor luggage.

Naturally, tourists don't want to overpay luggage fee, therefore they distribute their luggage so that it satisfies all airline requirements.

A certain tourist prepaid three luggage slots. Then he calculated the number of different ways K to distribute weight N among these three slots so that all luggage is packed, none of the slots are empty and all weights are integers. The order of the slots does not matter, so, for example, two distributions 2,  2,  1 and 2,  1,  2 are considered the same.

After landing, the tourist realised that the airline lost all his luggage! And while filling in a lost and found application, he found out that he does not remember the weight of each slot. He remembered only the fact that the number of ways K to pack the luggage was at least L and did not exceed R.

You need to calculate number of possible integer total weights N that could have been in the tourist's luggage.

The single line of input holds two integer numbers L and R (1 ≤ L ≤ R ≤ 10¹⁷): the minimum and maximum number of ways to distribule the luggage in three slots.

Output a single integer: the number of possible total weigths N that could have been carried by the tourist.

2 4

3

In the example, the tourist could have carried the total weight of 5, 6 or 7.