Sum of Multiples of K

Source: Phước Hưng OJ

Version: Phuoc Hung OJ Extended

Problem Statement

Given nonnegative n and positive k, sum all integers i in [1,n] divisible by k using a for loop and a 64-bit accumulator.

Input

n k, 0<=n<=1000000 and 1<=k<=1000000.

Output

The sum as an integer.

Subtasks

• Subtask 1 (20%): $n\le20$, $k\le5$.
• Subtask 2 (30%): $n\le1000$, $k\le100$.
• Subtask 3 (50%): $n\le10^6$, $k\le10^6$.

Examples

Example 1

Input

10 3

Output

18

Explanation

3+6+9=18.

Example 2

Input

0 1

Output

0

Explanation

The range is empty.