String Quartet

By Kay Akashi

Time: 1000 ms

Memory: 256000 kB

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Problem Statement

Kay has $4$ strings and lays them on an X-axis. String $i$ has its left end at $x = l_i$ and right end at $x = r_i$ . Now, find the length of line segment where all the $4$ strings are laid.

Constraints

$0 \leq l_i \lt r_i \leq 10$ .

All the input values are given as integers.

Input

The input contains $4$ lines, each of which has $l_i$ and $r_i$ .

Output

Output a single integer, the length of line segment where all $4$ strings overlap.

Examples

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Explanation

It is the line segment between $x = 5$ and $x = 8$ that satisfies the condition. Hence the length is $8 - 5 = 3$ .

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Output

Explanation

$x = 3$ satisfies the condition. However, note that the point has a length of $0$ .

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String Quartet

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