#include <bits/stdc++.h>

using namespace std;

int x[100000], y[100000];

int main() {
	int n, m;

	scanf("%d %d", &n, &m);

	for (int i = 0;i < m;++i)
		scanf("%d", &x[i]);

	sort(x, x + m);

	for (int i = 1;i < m;++i)
		y[i] = x[i] - x[i - 1];

	sort(y + 1, y + m, greater<int>());

	int tot = 0;
	for (int i = n;i < m;++i)
		tot += y[i];

	printf("%d", tot);

	return 0;
}
### Prompt

Please formulate 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 x[100000], y[100000];

int main() {
	int n, m;

	scanf("%d %d", &n, &m);

	for (int i = 0;i < m;++i)
		scanf("%d", &x[i]);

	sort(x, x + m);

	for (int i = 1;i < m;++i)
		y[i] = x[i] - x[i - 1];

	sort(y + 1, y + m, greater<int>());

	int tot = 0;
	for (int i = n;i < m;++i)
		tot += y[i];

	printf("%d", tot);

	return 0;
}
```