THỰC HÀNH

Given three positive integers ( m ), ( n ), and ( k ), count the number of integer pairs ((x, y)) that satisfy the following conditions:
( 0 \leq x \leq m ), ( 0 \leq y \leq n ), and ( x + y ) is divisible by ( k ).

Input:

• A single line containing three positive integers ( m ), ( n ), and ( k ), where ( k \leq 10^9 ), separated by spaces.

Output:

• Print the number of pairs that satisfy the given conditions.

Example:

Input:

6 8 3

Output:

21