Mandarins

Limits: 2 sec., 256 MiB

This statement was translated automatically from Ukrainian.

Marichka plans to buy mandarins for Zenyk.

Marichka knows that Zenyk will be upset if the number of mandarins is from \(l_1\) to \(r_1\) inclusively. Marichka herself will be upset if the number of mandarins is from \(l_2\) to \(r_2\) inclusively.

Marichka is wondering what is the minimum number of mandarins she can buy so that everyone is happy. Of course, she needs to buy at least one mandarin.

Input

The first line contains 2 integers \(l_1\) and \(r_1\).

The second line contains 2 integers \(l_2\) and \(r_2\).

Output

Output a single integer — the minimum number of mandarins Marichka can buy.

Constraints

\(1 \le l_1 < r_1 \le 10^9\),

\(1 \le l_2 < r_2 \le 10^9\).

Samples