Princess Heidi decided to give orders to all her K Rebel ship commanders in person. Unfortunately, she is currently travelling through hyperspace, and will leave it only at N specific moments t1, t2, ..., tN. The meetings with commanders must therefore start and stop at those times. Namely, each commander will board her ship at some time ti and disembark at some later time tj. Of course, Heidi needs to meet with all commanders, and no two meetings can be held during the same time. Two commanders cannot even meet at the beginnings/endings of the hyperspace jumps, because too many ships in one position could give out their coordinates to the enemy. 

Your task is to find minimum time that Princess Heidi has to spend on meetings, with her schedule satisfying the conditions above. 

Input

The first line contains two integers K, N (2 ≤ 2K ≤ N ≤ 500000, K ≤ 5000). The second line contains N distinct integers t1, t2, ..., tN (1 ≤ ti ≤ 109) representing the times when Heidi leaves hyperspace.

Output

Output only one integer: the minimum time spent on meetings. 

Examples

Input

2 5
1 4 6 7 12


Output

4


Input

3 6
6 3 4 2 5 1


Output

3


Input

4 12
15 7 4 19 3 30 14 1 5 23 17 25


Output

6

Note

In the first example, there are five valid schedules: [1, 4], [6, 7] with total time 4, [1, 4], [6, 12] with total time 9, [1, 4], [7, 12] with total time 8, [1, 6], [7, 12] with total time 10, and [4, 6], [7, 12] with total time 7. So the answer is 4.

In the second example, there is only 1 valid schedule: [1, 2], [3, 4], [5, 6].

For the third example, one possible schedule with total time 6 is: [1, 3], [4, 5], [14, 15], [23, 25].
import java.io.*;
import java.util.*;

public class E2 implements Runnable{
	public static void main (String[] args) {new Thread(null, new E2(), "_cf", 1 << 28).start();}

	public void run() {
		DeoxysS fs = new DeoxysS();
		PrintWriter out = new PrintWriter(System.out);
		System.err.println("Go!");

		int k = fs.nextInt();
		int n = fs.nextInt();
		int[] a = fs.nextIntArray(n); sort(a);
		int[] diffs = new int[n - 1];
		for(int i = 0; i < n - 1; i++) diffs[i] = a[i + 1] - a[i];
		Index[] b = new Index[n - 1];
		for(int i = 0; i < n - 1; i++) b[i] = new Index(i, diffs[i]);
		Arrays.sort(b, (x, y) -> Integer.compare(x.val, y.val));
		b = Arrays.copyOfRange(b, 0, Math.min(b.length, 3 * k + 100));
		Arrays.sort(b, (x, y) -> Integer.compare(x.idx, y.idx));

		long[] dp = new long[b.length + 2];
		long oo = (long)1e15;
		for(int ii = 0; ii < k; ii++) {
			long[] ndp = new long[dp.length]; Arrays.fill(ndp, oo);
			for(int i = b.length - 1; i >= 0; i--) {
				ndp[i] = Math.min(dp[i + 2] + b[i].val, ndp[i + 1]);
				if(i + 1 < b.length && b[i+1].idx-b[i].idx > 1) ndp[i] = Math.min(ndp[i], dp[i+1] + b[i].val);
			}
			dp = ndp;
		}
		out.println(dp[0]);
		
		out.close();
	}

	class Index {
		int idx, val;
		Index(int a, int b) { idx = a; val = b; }
		public String toString() { return "Idx " + idx + " Val " + val; }
	}

	void sort (int[] a) {
		int n = a.length;
		for(int i = 0; i < 50; i++) {
			Random r = new Random();
			int x = r.nextInt(n), y = r.nextInt(n);
			int temp = a[x];
			a[x] = a[y];
			a[y] = temp;
		}
		Arrays.sort(a);
	}

	class DeoxysS {
		public int BS = 1<<16;
		public char NC = (char)0;
		byte[] buf = new byte[BS];
		int bId = 0, size = 0;
		char c = NC;
		double num = 1;
		BufferedInputStream in;

		public DeoxysS() {
			in = new BufferedInputStream(System.in, BS);
		}

		public DeoxysS(String s) throws FileNotFoundException {
			in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
		}

		public char nextChar(){
			while(bId==size) {
				try {
					size = in.read(buf);
				}catch(Exception e) {
					return NC;
				}                
				if(size==-1)return NC;
				bId=0;
			}
			return (char)buf[bId++];
		}

		public int nextInt() {
			return (int)nextLong();
		}

		public long nextLong() {
			num=1;
			boolean neg = false;
			if(c==NC)c=nextChar();
			for(;(c<'0' || c>'9'); c = nextChar()) {
				if(c=='-')neg=true;
			}
			long res = 0;
			for(; c>='0' && c <='9'; c=nextChar()) {
				res = (res<<3)+(res<<1)+c-'0';
				num*=10;
			}
			return neg?-res:res;
		}

		public double nextDouble() {
			double cur = nextLong();
			return c!='.' ? cur:cur+nextLong()/num;
		}

		public String next() {
			StringBuilder res = new StringBuilder();
			while(c<=32)c=nextChar();
			while(c>32) {
				res.append(c);
				c=nextChar();
			}
			return res.toString();
		}

		public String nextLine() {
			StringBuilder res = new StringBuilder();
			while(c<=32)c=nextChar();
			while(c!='\n') {
				res.append(c);
				c=nextChar();
			}
			return res.toString();
		}

		public boolean hasNext() {
			if(c>32)return true;
			while(true) {
				c=nextChar();
				if(c==NC)return false;
				else if(c>32)return true;
			}
		}
		
		public int[] nextIntArray(int n) {
			int[] res = new int[n];
			for(int i = 0; i < n; i++) res[i] = nextInt();
			return res;
		}
		
	}

}