Map data structure
Find all possible values of product i * j, if the integer values of variables i and j vary for i from a to b and j from c to d (1 ≤ a, b, c, d ≤ 10).
One line contains 4 numbers a, b, c and d (a can be greater than b, c can be greater than d).
Print the number of possible product values.
1 10 1 10