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.*;
    import java.math.BigDecimal;
    import java.util.ArrayDeque;
    import java.util.Arrays;
    import java.util.InputMismatchException;
    import java.util.Queue;
    import java.io.*;
    import java.lang.reflect.Array;
    import java.math.BigInteger;
    import java.util.*;
    import java.io.BufferedReader;
    import java.io.IOException;
    import java.util.Collections;
    import java.io.InputStreamReader;
    import java.util.logging.SimpleFormatter;


        public class Main1 {






            public static void main(String[] args) {


                FastScanner in = new FastScanner();
                PrintWriter out = new PrintWriter(System.out);



                int n = in.nextInt() ;
                int k = in.nextInt() ;
                int a[] = in.readArray(n) ;
                int max = -1 ;

                if (k >= n){
                    System.out.println(a[n-1]);
                    return;
                }
                else {
                    int i = 0 ;
                    int j = 2*(n - k) - 1 ;

                    while (i < j){
                        max = Math.max(max , a[i]+a[j]) ;
                        i++ ;
                        j-- ;
                    }
                }


                System.out.println(Math.max(max , a[n-1]));
















                out.flush();
                out.close();

            }


            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;
            }






            static void updateRangeLazy(int tree[] , int lazy[] , int ss ,int se , int l , int r , int increment , int index){

                if (lazy[index] != 0 ){
                    tree[index] += lazy[index];

                    if (ss != se){
                        lazy[2*index]  +=  lazy[index];
                        lazy[2*index + 1]  +=  lazy[index];
                    }
                    lazy[index ] = 0 ;
                }

                if (ss > r && se< l )
                    return;

                if (ss >= l && se <= r) {
                    tree[index] += increment;


                    if (ss != se) {
                        lazy[2 * index] += increment;
                        lazy[2 * index + 1] += increment;
                    }
                    return;
                }

                int mid = (ss + se)/2 ;


                tree[index] =  Math.min( tree[2*index], tree[2*index + 1] ) ;

            }




            static class FastOutput implements AutoCloseable, Closeable, Appendable {
                private static final int THRESHOLD = 32 << 10;
                private final Writer os;
                private StringBuilder cache = new StringBuilder(THRESHOLD * 2);

                public FastOutput append(CharSequence csq) {
                    cache.append(csq);
                    return this;
                }

                public FastOutput append(CharSequence csq, int start, int end) {
                    cache.append(csq, start, end);
                    return this;
                }

                private void afterWrite() {
                    if (cache.length() < THRESHOLD) {
                        return;
                    }
                    flush();
                }

                public FastOutput(Writer os) {
                    this.os = os;
                }

                public FastOutput(OutputStream os) {
                    this(new OutputStreamWriter(os));
                }

                public FastOutput append(char c) {
                    cache.append(c);
                    afterWrite();
                    return this;
                }

                public FastOutput append(long c) {
                    cache.append(c);
                    afterWrite();
                    return this;
                }

                public FastOutput append(String c) {
                    cache.append(c);
                    afterWrite();
                    return this;
                }

                public FastOutput println() {
                    return append(System.lineSeparator());
                }

                public FastOutput flush() {
                    try {
    //            boolean success = false;
    //            if (stringBuilderValueField != null) {
    //                try {
    //                    char[] value = (char[]) stringBuilderValueField.get(cache);
    //                    os.write(value, 0, cache.length());
    //                    success = true;
    //                } catch (Exception e) {
    //                }
    //            }
    //            if (!success) {
                        os.append(cache);
    //            }
                        os.flush();
                        cache.setLength(0);
                    } catch (IOException e) {
                        throw new UncheckedIOException(e);
                    }
                    return this;
                }

                public void close() {
                    flush();
                    try {
                        os.close();
                    } catch (IOException e) {
                        throw new UncheckedIOException(e);
                    }
                }

                public String toString() {
                    return cache.toString();
                }

            }







            static class FastScanner {
                BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
                StringTokenizer st = new StringTokenizer("");

                String next() {
                    while (!st.hasMoreTokens())
                        try {
                            st = new StringTokenizer(br.readLine());
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    return st.nextToken();
                }

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

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


                long nextLong() {
                    return Long.parseLong(next());
                }
            }


        }







