Given N, М and K. All nubers are < = 109
Define value of matrix in row i and column j as (i + j) mod K where i < = N and j < = M
Given Q < = 2 * 105 queries of form Li, Lj, Ri, Rj and you need to find sum of elements from submatrix with upper-left corner (Li, Lj) and lower-right corner (Ri, Rj) module 109 + 7.
Some ideas? (There is a solution for this problem but it is not really clear to me, so I'm asking for maybe different ideas)
