Killer Sudoku #38

In each cell of the NxN grid, enter a number in the range 1–N. Each number must appear exactly once in each row and column, and in each grey and white block (but not in each region with a given number).
Additional rules: The sum of the numbers in a region must equal the given number.

Calculator gives all the valid combinations for a given sum and number of digits. You can also use the combination tables
Short manual