Problem Statement

We have $N+1$ integers: $10^{100}$, $10^{100}+1$, ..., $10^{100}+N$.

We will choose $K$ or more of these integers. Find the number of possible values of the sum of the chosen numbers, modulo $(10^9+7)$.

Constraints

• $1 \\leq N \\leq 2\\times 10^5$
• $1 \\leq K \\leq N+1$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$N$ $K$

Output

Print the number of possible values of the sum, modulo $(10^9+7)$.

Sample Input 1

3 2

Sample Output 1

10

The sum can take $10$ values, as follows:

• $(10^{100})+(10^{100}+1)=2\\times 10^{100}+1$
• $(10^{100})+(10^{100}+2)=2\\times 10^{100}+2$
• $(10^{100})+(10^{100}+3)=(10^{100}+1)+(10^{100}+2)=2\\times 10^{100}+3$
• $(10^{100}+1)+(10^{100}+3)=2\\times 10^{100}+4$
• $(10^{100}+2)+(10^{100}+3)=2\\times 10^{100}+5$
• $(10^{100})+(10^{100}+1)+(10^{100}+2)=3\\times 10^{100}+3$
• $(10^{100})+(10^{100}+1)+(10^{100}+3)=3\\times 10^{100}+4$
• $(10^{100})+(10^{100}+2)+(10^{100}+3)=3\\times 10^{100}+5$
• $(10^{100}+1)+(10^{100}+2)+(10^{100}+3)=3\\times 10^{100}+6$
• $(10^{100})+(10^{100}+1)+(10^{100}+2)+(10^{100}+3)=4\\times 10^{100}+6$

Sample Input 2

200000 200001

Sample Output 2

1

We must choose all of the integers, so the sum can take just $1$ value.

Sample Input 3

141421 35623

Sample Output 3

220280457