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Dreamoon and Sums

1000ms

262144K

Description:

Dreamoon loves summing up something for no reason. One day he obtains two integers a and b occasionally. He wants to calculate the sum of all nice integers. Positive integer x is called nice if $\text{[math]}$ and $\text{[math]}$ , where k is some integer number in range [1, a].

By $\text{[math]}$ we denote the quotient of integer division of x and y. By $\text{[math]}$ we denote the remainder of integer division of x and y. You can read more about these operations here: http://goo.gl/AcsXhT.

The answer may be large, so please print its remainder modulo 1 000 000 007 (10⁹ + 7). Can you compute it faster than Dreamoon?

Input:

The single line of the input contains two integers a, b (1 ≤ a, b ≤ 10⁷).

Output:

Print a single integer representing the answer modulo 1 000 000 007 (10⁹ + 7).

Sample Input:

1 1

Sample Output:

Sample Input:

2 2

Sample Output:

Note:

For the first sample, there are no nice integers because $\text{[math]}$ is always zero.

For the second sample, the set of nice integers is {3, 5}.

Informação

Codeforces

Provedor Codeforces

Código CF476C

Tags

math

Submetido 0

BOUA! 0

Taxa de BOUA's 0%

Datas 09/05/2023 08:54:06

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