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.util.*;
import java.io.*;
import java.math.*;

public class B{
	
	static int n,k,s[],res,b[];
	static void MainMethod()throws Exception{
		n=reader.nextInt(); k=reader.nextInt();
		s=new int[n]; int i,j; b=new int[k];
		for (i=0;i<n;i++) s[i]=reader.nextInt();
		res=s[n-1];
		if (k>=n){
			printer.print(res);
			halt();
		}
		for (i=0;i<k;i++) b[i]=s[n-1-i];
		j=k;
		for (i=n-k-1;i>=0;i--){
			j--;
			b[j]+=s[i];
			res=Math.max(res, b[j]);
		}
		printer.print(res);
	}
	public static void main(String[] args)throws Exception{
		MainMethod();
		printer.close();
	}
	static void halt(){
		printer.close();
		System.exit(0);
	}
	static PrintWriter printer=new PrintWriter(new OutputStreamWriter(System.out));
	static class reader{
		static BufferedReader bReader=new BufferedReader(new InputStreamReader(System.in));
		static StringTokenizer token=new StringTokenizer("");
		static String readNextLine() throws Exception{
			return bReader.readLine();
		}
		static String next() throws Exception{
			while (token.hasMoreTokens()==false){
				token=new StringTokenizer(bReader.readLine());
			}
			return token.nextToken();
		}
		static int nextInt()throws Exception{
			while (token.hasMoreTokens()==false){
				token=new StringTokenizer(bReader.readLine());
			}
			return Integer.parseInt(token.nextToken());
		}
		static long nextLong()throws Exception{
			while (token.hasMoreTokens()==false){
				token=new StringTokenizer(bReader.readLine());
			}
			return Long.parseLong(token.nextToken());
		}
		static double nextDouble()throws Exception{
			while (token.hasMoreTokens()==false){
				token=new StringTokenizer(bReader.readLine());
			}
			return Double.parseDouble(token.nextToken());
		}
	}
	static class MyMathCompute{
		static long [][] MatrixMultiplyMatrix(long [][] A, long [][] B, long mod) throws Exception{
			int n=A.length, m=B[0].length; 
			int p=A[0].length;
			int i,j,k;
			if (B.length!=p) throw new Exception("invalid matrix input");
			long [][] res=new long [n][m];
			for (i=0;i<n;i++) for (j=0;j<m;j++){
				if (A[i].length!=p) throw new Exception("invalid matrix input");
				res[i][j]=0;
				for (k=0;k<p;k++)
					res[i][j]=(res[i][j]+((A[i][k]*B[k][j])% mod))% mod;
			}
			return res;
		}
		static double [][] MatrixMultiplyMatrix(double [][] A, double [][] B ) throws Exception{
			int n=A.length, m=B[0].length; 
			int p=A[0].length;
			int i,j,k;
			if (B.length!=p) throw new Exception("invalid matrix input");
			double [][] res=new double [n][m];
			for (i=0;i<n;i++) for (j=0;j<m;j++){
				if (A[i].length!=p) throw new Exception("invalid matrix input");
				res[i][j]=0;
				for (k=0;k<p;k++)
					res[i][j]=res[i][j]+(A[i][k]*B[k][j]);
			}
			return res;
		}
		static long [][] MatrixPow(long [][] A,long n, long mod) throws Exception{
			if (n==1) return A;
			long [][] res=MatrixPow(A, n/2, mod);
			res=MatrixMultiplyMatrix(res, res, mod);
			if ((n % 2) == 1) res=MatrixMultiplyMatrix(A,res, mod);		
			return res;
		}
		static double [][] MatrixPow(double [][] A,long n) throws Exception{
			if (n==1) return A;
			double[][] res=MatrixPow(A, n/2);
			res=MatrixMultiplyMatrix(res, res);
			if ((n % 2) == 1) res=MatrixMultiplyMatrix(A,res);		
			return res;
		}
		static long pow(long a,long n,long mod){
			a= a % mod;
			if (n==0) return 1;
			long k=pow(a,n/2,mod);
			if ((n % 2)==0) return ((k*k)%mod);
			else return (((k*k) % mod)*a) % mod;
		}
		static double pow(double a,long n){
			if (n==0) return 1;
			double k=pow(a,n/2);
			if ((n % 2)==0) return (k*k);
			else return (((k*k) )*a) ;
		}
	}
}
