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 $${ \bmod ( x, b ) } \neq 0$$ and $$\frac{\operatorname{div}(x,b)}{\operatorname{mod}(x,b)} = k$$, where k is some integer number in range [1, a].
By $$\operatorname{div}(x,y)$$ we denote the quotient of integer division of x and y. By $$\operatorname{mod}(x,y)$$ 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 Format:
The single line of the input contains two integers a, b (1 ≤ a, b ≤ 107).
Output Format:
Print a single integer representing the answer modulo 1 000 000 007 (109 + 7).
Note:
For the first sample, there are no nice integers because $$\operatorname{mod}(x,1)$$ is always zero.
For the second sample, the set of nice integers is {3, 5}.