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.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.*;

public class popo {

    public static boolean prime[];
    public static ArrayList[] ad=new ArrayList[2555];
    public static ArrayList<Long> xor1,xor2;
    static int []min;
    static char [][]grid;
    static int []dx = {0,0,-1,1};
    static int []dy = {-1,1,0,0};
    static int []dx8 = {1,1,1,0,-1,-1,-1,0};
    static int []dy8 = {1,0,-1,-1,-1,0,1,1};
    static ArrayList<Point> aa;

    public static void main(String[] args) {
        InputReader in = new InputReader(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int n = in.nextInt();
        int k = in.nextInt();
        long []a = new long[n];
        long max = -1;
        for (int i=0;i<n;i++)
        {
            a[i] = in.nextLong();
            if(max<a[i])
            {
                max = a[i];
            }
        }
        if(k>=n)
        {
            out.println(max);
            out.close();
            return;
        }else
        {
              for (int i=0;i<2*(n-k);i++)
              {
                  max = Math.max(a[i]+a[2*(n-k)-1-i],max);
              }
        }
        out.println(max);
        out.close();
    }

    public static long modPow(long base, long exp, long mod) {
        base = base % mod;
        long result = 1;
        while(exp > 0)
        {
            if(exp % 2== 1)
            {
                result = (result * base) % mod;
                exp --;
            }
            else
            {
                base = (base * base) % mod;
                exp = exp >> 1;
            }

        }
        return result;
    }

    public static long mod = 1000000007, inf = 100000000000000000l;
    public static long fac[],inv[];
    public static void cal()
    {
        fac = new long[100001];
        inv = new long[100001];
        fac[0]=1;
        inv[0]=1;
        for(int i=1; i<=100000; i++)
        {
            fac[i]=(fac[i-1]*i)%mod;
            //  inv[i]=(inv[i-1]*modPow(i,mod-2,mod))%mod;

        }
    }
    public static long combination(long n, long r)
    {
        long k = (fac[(int) n]%mod*inv[(int) r]%mod)%mod;
        long p = inv[(int) (n-r)]%mod;
        long m = (k*p)%mod;
        return m;
    }


    public static class Point implements Comparable<Point> {

        long x, y;

        public Point(long start, long end) {
            this.x = start;
            this.y = end;
        }

        @Override
        public int hashCode() {
            int hash = 5;
            hash = (int) (47 * hash + this.x);
            hash = (int) (47 * hash + this.y);
            return hash;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final Point other = (Point) obj;
            if (this.x != other.x) {
                return false;
            }
            if (this.y != other.y) {
                return false;
            }
            return true;
        }

        @Override
        public int compareTo(Point o) {
            return Long.compare(x, o.x);
        }
    }
    static long setbits(long i)
    {
        long count = 0;
        while (i>0)
        {
            count += i & 1;
            i >>= 1;
        }
        return count;

    }

    static ArrayList<Long> sieveOfEratosthenes(int n)
    {
        // Create a boolean array "prime[0..n]" and initialize
        // all entries it as true. A value in prime[i] will
        // finally be false if i is Not a prime, else true.


        prime=new boolean[1000001];
        for(int i=0;i<n;i++)
            prime[i] = true;

        for(long p = 2; p*p <=n; p++)
        {
            // If prime[p] is not changed, then it is a prime
            if(prime[(int)p] == true)
            {
                // Update all multiples of p
                for(long i = p*2; i <= n; i += p) {
                    prime[(int) i] = false;
                }
            }
        }
        ArrayList<Long> aa=new ArrayList<>();
        for (long i=0;i<n;i++)
        {
            if(prime[(int)i])
                aa.add(i);
        }
        return aa;

        // Print all prime numbers
      /*  for(int i = 2; i <= n; i++)
        {
            if(prime[i] == true)
                System.out.print(i + " ");
        }
       */
    }

    static class InputReader {

        private InputStream stream;
        private byte[] buf = new byte[8192];
        private int curChar, snumChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int snext() {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars) {
                curChar = 0;
                try {
                    snumChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public int nextInt() {
            int c = snext();
            while (isSpaceChar(c))
                c = snext();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = snext();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public long nextLong() {
            int c = snext();
            while (isSpaceChar(c))
                c = snext();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = snext();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public int[] nextIntArray(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        public String readString() {
            int c = snext();
            while (isSpaceChar(c))
                c = snext();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = snext();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
}