description: Alice has an integer sequence a of length n and all elements are different. She will choose a subsequence of a of length m, and defines the value of a subsequence a_{b_1},a_{b_2},…,a_{b_m} as $$$∑_{i = 1}^m (m ⋅ a_{b_i}) - ∑_{i = 1}^m ∑_{j = 1}^m f(min(b_i, b_j), max(b_i, b_j)), where f(i, j) denotes \min(a_i, a_{i + 1}, \ldots, a_j)$$$.
  
  Alice wants you to help her to maximize the value of the subsequence she choose.
  
  A sequence s is a subsequence of a sequence t if s can be obtained from t by deletion of several (possibly, zero or all) elements.
  
  Input
  
  The first line contains two integers n and m (1 ≤ m ≤ n ≤ 4000).
  
  The second line contains n distinct integers a_1, a_2, …, a_n (1 ≤ a_i < 2^{31}).
  
  Output
  
  Print the maximal value Alice can get.
  
  Examples
  
  Input
  
  
  6 4
  15 2 18 12 13 4
  
  
  Output
  
  
  100
  
  
  Input
  
  
  11 5
  9 3 7 1 8 12 10 20 15 18 5
  
  
  Output
  
  
  176
  
  
  Input
  
  
  1 1
  114514
  
  
  Output
  
  
  0
  
  
  Input
  
  
  2 1
  666 888
  
  
  Output
  
  
  0
  
  Note
  
  In the first example, Alice can choose the subsequence [15, 2, 18, 13], which has the value 4 ⋅ (15 + 2 + 18 + 13) - (15 + 2 + 2 + 2) - (2 + 2 + 2 + 2) - (2 + 2 + 18 + 12) - (2 + 2 + 12 + 13) = 100. In the second example, there are a variety of subsequences with value 176, and one of them is [9, 7, 12, 20, 18].
solution: //package round745;
  import java.io.*;
  import java.util.*;
  
  public class D {
  	InputStream is;
  	FastWriter out;
  	String INPUT = "";
  	
  	void solve()
  	{
  		int n = ni(), m = ni();
  		int[] a = na(n);
  		int[][] ai = new int[n][];
  		for(int i = 0;i < n;i++){
  			ai[i] = new int[]{a[i], i};
  		}
  		Arrays.sort(ai, Comparator.comparingInt(x -> x[0]));
  		long[] ret = dfs(0, n, 0, m, ai, a);
  		out.println(ret[m]);
  	}
  
  	// (18+13)*4-18-13-12*2
  
  	long[] dfs(int l, int r, int pos, int m, int[][] ai, int[] a)
  	{
  		if(r-l == 1){
  			long[] ret = new long[2];
  			ret[1] = (long)m*a[l] - a[l];
  			return ret;
  		}
  		if(r-l == 0){
  			return new long[1];
  		}
  
  		while(!(l <= ai[pos][1] && ai[pos][1] < r))pos++;
  		int h = ai[pos][1];
  		long[] L = dfs(l, h, pos, m, ai, a);
  		long[] R = dfs(h+1, r, pos, m, ai, a);
  
  		long[] ret = new long[L.length+R.length];
  		Arrays.fill(ret, Long.MIN_VALUE / 2);
  		for(int i = 0;i <= L.length-1;i++){
  			for(int j = 0;j <= R.length-1;j++){
  				ret[i+j] = Math.max(ret[i+j], L[i] + R[j] - ai[pos][0] * (long)i * j * 2);
  				ret[i+j+1] = Math.max(ret[i+j+1], L[i] + R[j] + (long)m*ai[pos][0] - ai[pos][0] * ((long)i * j * 2 + 2 * i + 2 * j + 1));
  			}
  		}
  //		tr(l, h, r, L, R, ret);
  		return ret;
  	}
  
  
  	void run() throws Exception
  	{
  		is = oj ? System.in : new ByteArrayInputStream(INPUT.getBytes());
  		out = new FastWriter(System.out);
  		
  		long s = System.currentTimeMillis();
  		solve();
  		out.flush();
  		tr(System.currentTimeMillis()-s+"ms");
  	}
  	
  	public static void main(String[] args) throws Exception { new D().run(); }
  	
  	private byte[] inbuf = new byte[1024];
  	public int lenbuf = 0, ptrbuf = 0;
  	
  	private int readByte()
  	{
  		if(lenbuf == -1)throw new InputMismatchException();
  		if(ptrbuf >= lenbuf){
  			ptrbuf = 0;
  			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
  			if(lenbuf <= 0)return -1;
  		}
  		return inbuf[ptrbuf++];
  	}
  	
  	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
  	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
  	
  	private double nd() { return Double.parseDouble(ns()); }
  	private char nc() { return (char)skip(); }
  	
  	private String ns()
  	{
  		int b = skip();
  		StringBuilder sb = new StringBuilder();
  		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
  			sb.appendCodePoint(b);
  			b = readByte();
  		}
  		return sb.toString();
  	}
  	
  	private char[] ns(int n)
  	{
  		char[] buf = new char[n];
  		int b = skip(), p = 0;
  		while(p < n && !(isSpaceChar(b))){
  			buf[p++] = (char)b;
  			b = readByte();
  		}
  		return n == p ? buf : Arrays.copyOf(buf, p);
  	}
  
  	private int[] na(int n)
  	{
  		int[] a = new int[n];
  		for(int i = 0;i < n;i++)a[i] = ni();
  		return a;
  	}
  
  	private long[] nal(int n)
  	{
  		long[] a = new long[n];
  		for(int i = 0;i < n;i++)a[i] = nl();
  		return a;
  	}
  
  	private char[][] nm(int n, int m) {
  		char[][] map = new char[n][];
  		for(int i = 0;i < n;i++)map[i] = ns(m);
  		return map;
  	}
  
  	private int[][] nmi(int n, int m) {
  		int[][] map = new int[n][];
  		for(int i = 0;i < n;i++)map[i] = na(m);
  		return map;
  	}
  
  	private int ni() { return (int)nl(); }
  
  	private long nl()
  	{
  		long num = 0;
  		int b;
  		boolean minus = false;
  		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
  		if(b == '-'){
  			minus = true;
  			b = readByte();
  		}
  
  		while(true){
  			if(b >= '0' && b <= '9'){
  				num = num * 10 + (b - '0');
  			}else{
  				return minus ? -num : num;
  			}
  			b = readByte();
  		}
  	}
  
  	public static class FastWriter
  	{
  		private static final int BUF_SIZE = 1<<13;
  		private final byte[] buf = new byte[BUF_SIZE];
  		private final OutputStream out;
  		private int ptr = 0;
  
  		private FastWriter(){out = null;}
  
  		public FastWriter(OutputStream os)
  		{
  			this.out = os;
  		}
  
  		public FastWriter(String path)
  		{
  			try {
  				this.out = new FileOutputStream(path);
  			} catch (FileNotFoundException e) {
  				throw new RuntimeException("FastWriter");
  			}
  		}
  
  		public FastWriter write(byte b)
  		{
  			buf[ptr++] = b;
  			if(ptr == BUF_SIZE)innerflush();
  			return this;
  		}
  
  		public FastWriter write(char c)
  		{
  			return write((byte)c);
  		}
  
  		public FastWriter write(char[] s)
  		{
  			for(char c : s){
  				buf[ptr++] = (byte)c;
  				if(ptr == BUF_SIZE)innerflush();
  			}
  			return this;
  		}
  
  		public FastWriter write(String s)
  		{
  			s.chars().forEach(c -> {
  				buf[ptr++] = (byte)c;
  				if(ptr == BUF_SIZE)innerflush();
  			});
  			return this;
  		}
  
  		private static int countDigits(int l) {
  			if (l >= 1000000000) return 10;
  			if (l >= 100000000) return 9;
  			if (l >= 10000000) return 8;
  			if (l >= 1000000) return 7;
  			if (l >= 100000) return 6;
  			if (l >= 10000) return 5;
  			if (l >= 1000) return 4;
  			if (l >= 100) return 3;
  			if (l >= 10) return 2;
  			return 1;
  		}
  
  		public FastWriter write(int x)
  		{
  			if(x == Integer.MIN_VALUE){
  				return write((long)x);
  			}
  			if(ptr + 12 >= BUF_SIZE)innerflush();
  			if(x < 0){
  				write((byte)'-');
  				x = -x;
  			}
  			int d = countDigits(x);
  			for(int i = ptr + d - 1;i >= ptr;i--){
  				buf[i] = (byte)('0'+x%10);
  				x /= 10;
  			}
  			ptr += d;
  			return this;
  		}
  
  		private static int countDigits(long l) {
  			if (l >= 1000000000000000000L) return 19;
  			if (l >= 100000000000000000L) return 18;
  			if (l >= 10000000000000000L) return 17;
  			if (l >= 1000000000000000L) return 16;
  			if (l >= 100000000000000L) return 15;
  			if (l >= 10000000000000L) return 14;
  			if (l >= 1000000000000L) return 13;
  			if (l >= 100000000000L) return 12;
  			if (l >= 10000000000L) return 11;
  			if (l >= 1000000000L) return 10;
  			if (l >= 100000000L) return 9;
  			if (l >= 10000000L) return 8;
  			if (l >= 1000000L) return 7;
  			if (l >= 100000L) return 6;
  			if (l >= 10000L) return 5;
  			if (l >= 1000L) return 4;
  			if (l >= 100L) return 3;
  			if (l >= 10L) return 2;
  			return 1;
  		}
  
  		public FastWriter write(long x)
  		{
  			if(x == Long.MIN_VALUE){
  				return write("" + x);
  			}
  			if(ptr + 21 >= BUF_SIZE)innerflush();
  			if(x < 0){
  				write((byte)'-');
  				x = -x;
  			}
  			int d = countDigits(x);
  			for(int i = ptr + d - 1;i >= ptr;i--){
  				buf[i] = (byte)('0'+x%10);
  				x /= 10;
  			}
  			ptr += d;
  			return this;
  		}
  
  		public FastWriter write(double x, int precision)
  		{
  			if(x < 0){
  				write('-');
  				x = -x;
  			}
  			x += Math.pow(10, -precision)/2;
  			//		if(x < 0){ x = 0; }
  			write((long)x).write(".");
  			x -= (long)x;
  			for(int i = 0;i < precision;i++){
  				x *= 10;
  				write((char)('0'+(int)x));
  				x -= (int)x;
  			}
  			return this;
  		}
  
  		public FastWriter writeln(char c){
  			return write(c).writeln();
  		}
  
  		public FastWriter writeln(int x){
  			return write(x).writeln();
  		}
  
  		public FastWriter writeln(long x){
  			return write(x).writeln();
  		}
  
  		public FastWriter writeln(double x, int precision){
  			return write(x, precision).writeln();
  		}
  
  		public FastWriter write(int... xs)
  		{
  			boolean first = true;
  			for(int x : xs) {
  				if (!first) write(' ');
  				first = false;
  				write(x);
  			}
  			return this;
  		}
  
  		public FastWriter write(long... xs)
  		{
  			boolean first = true;
  			for(long x : xs) {
  				if (!first) write(' ');
  				first = false;
  				write(x);
  			}
  			return this;
  		}
  
  		public FastWriter writeln()
  		{
  			return write((byte)'\n');
  		}
  
  		public FastWriter writeln(int... xs)
  		{
  			return write(xs).writeln();
  		}
  
  		public FastWriter writeln(long... xs)
  		{
  			return write(xs).writeln();
  		}
  
  		public FastWriter writeln(char[] line)
  		{
  			return write(line).writeln();
  		}
  
  		public FastWriter writeln(char[]... map)
  		{
  			for(char[] line : map)write(line).writeln();
  			return this;
  		}
  
  		public FastWriter writeln(String s)
  		{
  			return write(s).writeln();
  		}
  
  		private void innerflush()
  		{
  			try {
  				out.write(buf, 0, ptr);
  				ptr = 0;
  			} catch (IOException e) {
  				throw new RuntimeException("innerflush");
  			}
  		}
  
  		public void flush()
  		{
  			innerflush();
  			try {
  				out.flush();
  			} catch (IOException e) {
  				throw new RuntimeException("flush");
  			}
  		}
  
  		public FastWriter print(byte b) { return write(b); }
  		public FastWriter print(char c) { return write(c); }
  		public FastWriter print(char[] s) { return write(s); }
  		public FastWriter print(String s) { return write(s); }
  		public FastWriter print(int x) { return write(x); }
  		public FastWriter print(long x) { return write(x); }
  		public FastWriter print(double x, int precision) { return write(x, precision); }
  		public FastWriter println(char c){ return writeln(c); }
  		public FastWriter println(int x){ return writeln(x); }
  		public FastWriter println(long x){ return writeln(x); }
  		public FastWriter println(double x, int precision){ return writeln(x, precision); }
  		public FastWriter print(int... xs) { return write(xs); }
  		public FastWriter print(long... xs) { return write(xs); }
  		public FastWriter println(int... xs) { return writeln(xs); }
  		public FastWriter println(long... xs) { return writeln(xs); }
  		public FastWriter println(char[] line) { return writeln(line); }
  		public FastWriter println(char[]... map) { return writeln(map); }
  		public FastWriter println(String s) { return writeln(s); }
  		public FastWriter println() { return writeln(); }
  	}
  
  	public void trnz(int... o)
  	{
  		for(int i = 0;i < o.length;i++)if(o[i] != 0)System.out.print(i+":"+o[i]+" ");
  		System.out.println();
  	}
  
  	// print ids which are 1
  	public void trt(long... o)
  	{
  		Queue<Integer> stands = new ArrayDeque<>();
  		for(int i = 0;i < o.length;i++){
  			for(long x = o[i];x != 0;x &= x-1)stands.add(i<<6|Long.numberOfTrailingZeros(x));
  		}
  		System.out.println(stands);
  	}
  
  	public void tf(boolean... r)
  	{
  		for(boolean x : r)System.out.print(x?'#':'.');
  		System.out.println();
  	}
  
  	public void tf(boolean[]... b)
  	{
  		for(boolean[] r : b) {
  			for(boolean x : r)System.out.print(x?'#':'.');
  			System.out.println();
  		}
  		System.out.println();
  	}
  
  	public void tf(long[]... b)
  	{
  		if(INPUT.length() != 0) {
  			for (long[] r : b) {
  				for (long x : r) {
  					for (int i = 0; i < 64; i++) {
  						System.out.print(x << ~i < 0 ? '#' : '.');
  					}
  				}
  				System.out.println();
  			}
  			System.out.println();
  		}
  	}
  
  	public void tf(long... b)
  	{
  		if(INPUT.length() != 0) {
  			for (long x : b) {
  				for (int i = 0; i < 64; i++) {
  					System.out.print(x << ~i < 0 ? '#' : '.');
  				}
  			}
  			System.out.println();
  		}
  	}
  
  	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
  	private void tr(Object... o) { if(!oj)System.out.println(Arrays.deepToString(o)); }
  }
  