Kevin Sun wants to move his precious collection of n cowbells from Naperthrill to Exeter, where there is actually grass instead of corn. Before moving, he must pack his cowbells into k boxes of a fixed size. In order to keep his collection safe during transportation, he won't place more than two cowbells into a single box. Since Kevin wishes to minimize expenses, he is curious about the smallest size box he can use to pack his entire collection. 

Kevin is a meticulous cowbell collector and knows that the size of his i-th (1 ≤ i ≤ n) cowbell is an integer si. In fact, he keeps his cowbells sorted by size, so si - 1 ≤ si for any i > 1. Also an expert packer, Kevin can fit one or two cowbells into a box of size s if and only if the sum of their sizes does not exceed s. Given this information, help Kevin determine the smallest s for which it is possible to put all of his cowbells into k boxes of size s.

Input

The first line of the input contains two space-separated integers n and k (1 ≤ n ≤ 2·k ≤ 100 000), denoting the number of cowbells and the number of boxes, respectively.

The next line contains n space-separated integers s1, s2, ..., sn (1 ≤ s1 ≤ s2 ≤ ... ≤ sn ≤ 1 000 000), the sizes of Kevin's cowbells. It is guaranteed that the sizes si are given in non-decreasing order.

Output

Print a single integer, the smallest s for which it is possible for Kevin to put all of his cowbells into k boxes of size s.

Examples

Input

2 1
2 5


Output

7


Input

4 3
2 3 5 9


Output

9


Input

3 2
3 5 7


Output

8

Note

In the first sample, Kevin must pack his two cowbells into the same box. 

In the second sample, Kevin can pack together the following sets of cowbells: {2, 3}, {5} and {9}.

In the third sample, the optimal solution is {3, 5} and {7}.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Solution {

//		public static final double eps = 1e-9;
//		public static final int mod = 1000000007;
//		public static final double pi = 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679;
//		public static final int sievesize = (int) (1e7 + 10);
//		public static boolean[] prime;
//		public static final int dx[] = {1, -1, 0, 0};
//		public static final int dy[] = {0, 0, 1, -1};

	public static void main(String[] args) throws IOException {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		OutputWriter out = new OutputWriter(outputStream);
		Task solver = new Task();
		solver.solve(1, in, out);
		out.close();
	}

	static class Task {

		public void solve(int testNumber, InputReader in, OutputWriter out) throws IOException {
			int n = in.nextInt(), k = in.nextInt();
			int[] arr = in.nextIntArray(n);
			int max = Integer.MIN_VALUE;
			if (k >= n) {
				for (int i = 0; i < n; i++)
					max = Math.max(max, arr[i]);
			}
			else {
				int si = 2 * k - n, i = 0;
				while (i < si) {
					max = Math.max(max, arr[n - i - 1]);
					i++;
				}
				si =  2 * k - n;
				si = n - si;
				for (i = 0; i < si / 2; i++)
					max = Math.max(max, arr[i] + arr[si - i - 1]);
			}
			out.println(max);
		}
		
//		static class Node {
//			int data;
//			Node next;
//			
//			public Node(int data) {
//				this.data = data;
//				next = null;
//			}
//		}

//		static class Node {
//			String name;
//			LinkedList<Node> list;
//			
//			public Node(String name) {
//				this.name = name;
//				list = new LinkedList<>();
//			}
//		}
//        
		static class Pair<T> {   	
	      	T first, second;
		        	
		    public Pair(T first, T second) {
	    		this.first = first;
				this.second = second;
			}
	    }
	}

	//	public static int[] shuffle(int arr[], Random gen) {
	//		for(int i = 0, n = arr.length; i < n; i++)
	//		{
	//			int index = gen.nextInt(n - i) + i;
	//			int temp = arr[i];
	//			arr[i] = arr[index];
	//			arr[index] = temp;
	//		}
	//		return arr;
	//	}
	//
	//	public static boolean triangle(long a, long b, long c){
	//	    return ((a+b) > c && (b+c) >a && (a+c) > b);
	//	}
	//		
	//	public static boolean isPerfectSquare(long n){
	//		if (n < 0) 
	//	    	return false;
	//	    long test = (long) (Math.sqrt(n) + 0.5);
	//	    return test*test == n;
	//	}
	//		
	//	public static int isnum(char s){
	//		if(s=='1' || s=='2' || s=='3' || s=='4' || s=='5' || s=='6' || s=='7' || s=='8' || s=='9' || s=='0') 
	//	    	return 1; 
	//		return 0;
	//	}
	//		
	//	public static long nextPowerOf2(long n){
	//	    n--;
	//	    n |= n >> 1;
	//	    n |= n >> 2;
	//	    n |= n >> 4;
	//	    n |= n >> 8;
	//	    n |= n >> 16;
	//	    n++;
	//	    return n;
	//	}
	//		
//		public static int gcd(int a, int b){
//		    int t; 
//		    while (b > 0){ 
//		    	a = a % b; 
//		    	t = a; 
//		    	a = b; 
//		    	b = t; 
//	    	}
//		    return a;
//		}
	//		
	//	public static void sieve(int n){
	//		prime=new boolean[sievesize+1];
	//		Arrays.fill(prime, true);
	//	    long x, y; 
	//	    for(x = 2; x * x <= sievesize; x++)
	//	    { 
	//	    	if(prime[(int) x])
	//	    		for(y = x * 2; y <= sievesize; y += x) 
	//	    			prime[(int) y]=false; 
	//	    }
	//	}

	static class InputReader {
		public BufferedReader reader;
		public StringTokenizer tokenizer;

		public InputReader(InputStream stream) {
			reader = new BufferedReader(new InputStreamReader(stream), 32768);
			tokenizer = null;
		}

		public String next() {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			return tokenizer.nextToken();
		}

		public int nextInt() {
			return Integer.parseInt(next());
		}

		public long nextLong() {
			return Long.parseLong(next());
		}
		
		public char nextChar() {
			return next().charAt(0);
		}
		
		public float nextFloat() {
			return Float.parseFloat(next());
		}
		
		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public int[] nextIntArray(int size) {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			int[] arr=new int[size];
			for(int i = 0; i < size; i++) 
				arr[i] = Integer.parseInt(tokenizer.nextToken());
			return arr;
		}

		public long[] nextLongArray(int size) {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			long[] arr=new long[size];
			for(int i = 0; i < size; i++) 
				arr[i] = Long.parseLong(tokenizer.nextToken());
			return arr;
		}
		
		public float[] nextFloatArray(int size) {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			float[] arr=new float[size];
			for(int i = 0; i < size; i++) 
				arr[i] = Float.parseFloat(tokenizer.nextToken());
			return arr;
		}

		public double[] nextDoubleArray(int size) {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			double[] arr=new double[size];
			for(int i = 0; i < size; i++) 
				arr[i] = Double.parseDouble(tokenizer.nextToken());
			return arr;
		}

		public String[] nextStringArray(int size) throws IOException {
			String[] arr=new String[size];
			for(int i = 0; i < size; i++) 
				arr[i] = reader.readLine();
			return arr;
		}

		public char[] nextCharArray(int size) throws IOException {
			return reader.readLine().toCharArray();
		}
	}

	static class OutputWriter {
		public PrintWriter pw;

		public OutputWriter(OutputStream stream) {
			pw = new PrintWriter(stream);
		}
		
		public void println() {
			pw.println();
		}

		public void println(Object str) {
			pw.println(str);
		}

		public void print(Object str) {
			pw.print(str + " ");
		}

		public void close() {
			pw.close();
		}

		public void flush() {
			pw.flush();
		}

		public void printStringArray(String[] arr) {
			for(int i = 0; i < arr.length; i++)
				pw.println(arr[i]);
		}

		public void printIntArray(int[] arr) {
			for(int i = 0; i < arr.length; i++)
				pw.print(arr[i] + " ");
		}

		public void printLongArray(long[] arr) {
			for(int i = 0; i < arr.length; i++)
				pw.print(arr[i] + " ");
		}

		public void printCharArray(char[] arr) {
			for(int i = 0; i < arr.length; i++)
				pw.print(arr[i] + " ");
		}

		public void printFloatArray(float[] arr) {
			for(int i = 0; i < arr.length; i++)
				pw.print(arr[i] + " ");
		}

		public void printDoubleArray(double[] arr) {
			for(int i = 0; i < arr.length; i++)
				pw.print(arr[i] + " ");
		}
	}
}