Competitions

# Nails

Some nails are hammered on a straight plank. Any two nails can be joined by a thread. Connect some pairs of nails with a thread, so that to each nail will be tied with at least one thread, and the total length of all threads will be minimal.

#### Input

The first line contains the number of nails n (1 < n100). The next line contains n numbers - the coordinates of all the nails (non-negative integers not exceeding 10000).

#### Output

Print the minimum total length of all threads.

Time limit 1 second
Memory limit 128 MiB
Input example #1
5
4 10 0 12 2

Output example #1
6

Input example #3
10
2816 5839 8802 2517 6414 8995 2478 682 7667 4980 
Output example #3
4400