You are given two positive integers \(l\) and \(r\) with \(l \le r\). Compute the sum of the \(r - l + 1\) integers \(l, l+1, \ldots, r\) modulo \(2^{64}\).

Input

The input consists of two integers \(l\) and \(r\) (\(1 \le l \le r \le 10^{10}\)).

Output

Output a single integer representing the required value.

Sample Input 1

1 100

Sample Output 1

5050

Sample Input 2

1 10000000000

Sample Output 2

13106511857580896768