Problems

# Interesting Product

# Interesting Product

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**).

#### Input

One line contains **4** numbers **a**, **b**, **c** and **d** (**a** can be greater than **b**, **c** can be greater than **d**).

#### Output

Print the number of possible product values.

Input example #1

1 10 1 10

Output example #1

42