Saya and Kudo go shopping together.

You can assume the street as a straight line, while the shops are some points on the line.

They park their car at the leftmost shop, visit all the shops from left to right, and go back to their car.

Your task is to calculate the length of their route.

The input consists of several test cases.

The first line of input in each test case contains one integer N (0<N<100001), represents the number of shops.

The next line contains N integers, describing the situation of the shops. You can assume that the situations of the shops are non-negative integer and smaller than 2^30.

The last case is followed by a line containing one zero.

For each test case, print the length of their shopping route.