Kendoku

Kendoku (KenKen, CalcuDoku) is a logic puzzle. Write a number in each cell so that the results of all the given calculations are correct.

Rules: Enter a number from the range 1~N in each cell of the NxN grid. Each number must appear exactly once in each row and column (but not in each region).
The numbers in a region must be used to calculate the specified result using the specified operation (addition, subtraction, multiplication, division).
If no operation is specified, any operation can be used.