# Cutting a stick

You have to cut a wood stick into pieces. The most affordable company, The Analog Cutting Machinery, Inc. (ACM), charges money according to the length of the stick being cut. Their procedure of work requires that they only make one cut at a time.

It is easy to notice that different selections in the order of cutting can led to different prices. For example, consider a stick of length $10$ meters that has to be cut at $2,4$ and $7$ meters from one end. There are several choices. One can be cutting first at $2$, then at $4$, then at $7$. This leads to a price of $10+8+6=24$ because the first stick was of $10$ meters, the resulting of $8$ and the last one of $6$. Another choice could be cutting at $4$, then at $2$, then at $7$. This would lead to a price of $10+4+6=20$, which is a better price.

Your boss trusts your computer abilities to find out the minimum cost for cutting a given stick.

## Input

Consist of several cases. The first line of each test case will contain a positive number $l(l<1000)$ that represents the length of the stick to be cut. The next line will contain the number $n(n<50)$ of cuts to be made.

The next line consists of $n$ positive numbers $c_{i}(0<c_{i}<l)$ representing the places where the cuts have to be done, given in strictly increasing order. An input case with $l=0$ will represent the end of the input.

## Output

You have to print the cost of the optimal solution of the cutting problem, that is the minimum cost of cutting the given stick. Format the output as shown below.