URI Online Judge | 1805 | [P1]

Natural Sum

By Caio Russi, UNOESTE BR Brazil

Timelimit: 1

One natural number is a non-negative integer (0, 1, 2, 3, 4, 5,...). Your task in this problem is to calculate the sum of the natural numbers that are present in a given interval [A, B] including.

For instance, the sum of the natural numbers in the range [2, 5] is 14 = (2 + 3 + 4 + 5).

Input

The test case contains two integers A e B (1 ≤ AB ≤ 109), representing the lower limit and the upper respectively.

Output

For each test, the output consists of one line containing the sum of natural numbers in the range.

Input Sample Output Sample

1 5

15

1 1000

500500

10 20

165