B"Like any unknown mathematician, Yuri has favourite numbers: A , B , C , and D , where A <= q B <= q C <= q D . Yuri also likes triangles and once he thought: how many non-degenerate triangles with integer sides x , y , and z exist, such that A <= q x <= q B <= q y <= q C <= q z <= q D holds? Yuri is preparing problems for a new contest now, so he is very busy. That's why he asked you to calculate the number of triangles with described property. The triangle is called non-degenerate if and only if its vertices are not collinear. The first line contains four integers: A , B , C and D ( 1 <= q A <= q B <= q C <= q D <= q 5 cdot 10^5 ) -- Yuri's favourite numbers. Print the number of non-degenerate triangles with integer sides x , y , and z such that the inequality A <= q x <= q B <= q y <= q C <= q z <= q D holds. In the first example Yuri can make up triangles with sides (1, 3, 3) , (2, 2, 3) , (2, 3, 3) and (2, 3, 4) . In the second example Yuri can make up triangles with sides (1, 2, 2) , (2, 2, 2) and (2, 2, 3) . In the third example Yuri can make up only one equilateral triangle with sides equal to 5 cdot 10^5 . "...