#include "bits/stdc++.h"
using namespace std;

int main()
{
	int N, M, sum = 0;
	cin >> N >> M;
	vector<int> L(M);
	vector<int> abs(M-1);

	for (int i = 0; i < M; i++){
		cin >> L[i];
	}
	sort(L.begin(), L.end());
	
	for (int i = 0; i < M-1; i++) {
		abs[i] = L[i+1] - L[i];
	}
	sort(abs.begin(), abs.end());

	for (int i = 0; i < M-N; i++) {
		sum += abs[i];
	}

	cout << sum;
	
	return 0;
}
### Prompt

Your task is to create a cpp solution to the following problem:

We will play a one-player game using a number line and N pieces.

First, we place each of these pieces at some integer coordinate.

Here, multiple pieces can be placed at the same coordinate.

Our objective is to visit all of the M coordinates X_1, X_2, ..., X_M with these pieces, by repeating the following move:

Move: Choose a piece and let x be its coordinate. Put that piece at coordinate x+1 or x-1.

Note that the coordinates where we initially place the pieces are already regarded as visited.

Find the minimum number of moves required to achieve the objective.

Constraints

* All values in input are integers.
* 1 \leq N \leq 10^5
* 1 \leq M \leq 10^5
* -10^5 \leq X_i \leq 10^5
* X_1, X_2, ..., X_M are all different.

Input

Input is given from Standard Input in the following format:


N M
X_1 X_2 ... X_M


Output

Find the minimum number of moves required to achieve the objective.

Examples

Input

2 5
10 12 1 2 14


Output

5


Input

3 7
-10 -3 0 9 -100 2 17


Output

19


Input

100 1
-100000


Output

0

### Response

```cpp
#include "bits/stdc++.h"
using namespace std;

int main()
{
	int N, M, sum = 0;
	cin >> N >> M;
	vector<int> L(M);
	vector<int> abs(M-1);

	for (int i = 0; i < M; i++){
		cin >> L[i];
	}
	sort(L.begin(), L.end());
	
	for (int i = 0; i < M-1; i++) {
		abs[i] = L[i+1] - L[i];
	}
	sort(abs.begin(), abs.end());

	for (int i = 0; i < M-N; i++) {
		sum += abs[i];
	}

	cout << sum;
	
	return 0;
}
```