Interesting Product#916

Interesting Product

1 second

128 megabytes

Very easy

Determine all possible unique values of the product $i \cdot j$ i \cdot j, where the integer variables $i$ and $j$ range from $a$ to $b$ , and $c$ to $d$ , respectively.

$1 \leq a, b, c, d \leq 10$ 1 \leq a, b, c, d \leq 10. Note that $a$ may be greater than $b$ , and $c$ may be greater than $d$ .

Input

One line contains four integers $a$ , $b$ , $c$ , and $d$ .

Output

Print the number of unique possible values of the product.

Examples

Example 1

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Example 2

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i \cdot j

1 \leq a, b, c, d \leq 10