Problem:
Score : 400 points

Problem Statement

One day, Niwango-kun, an employee of Dwango Co., Ltd., found an integer sequence (a_1, ..., a_N) of length N.
He is interested in properties of the sequence a.

For a nonempty contiguous subsequence a_l, ..., a_r (1 \leq l \leq r \leq N) of the sequence a, its beauty is defined as a_l + ... + a_r. Niwango-kun wants to know the maximum possible value of the bitwise AND of the beauties of K nonempty contiguous subsequences among all N(N+1)/2 nonempty contiguous subsequences. (Subsequences may share elements.)

Find the maximum possible value for him.

Constraints

2 \leq N \leq 1000

1 \leq a_i \leq 10^9

1 \leq K \leq N(N+1)/2

All numbers given in input are integers

Input

Input is given from Standard Input in the following format:

N K
a_1 a_2 ... a_N

Output

Print the answer.

Sample Input 1

4 2
2 5 2 5

Sample Output 1

12

There are 10 nonempty contiguous subsequences of a. Let us enumerate them:

contiguous subsequences starting from the first element: \{2\}, \{2, 5\}, \{2, 5, 2\}, \{2, 5, 2, 5\}

contiguous subsequences starting from the second element: \{5\}, \{5, 2\}, \{5, 2, 5\}

contiguous subsequences starting from the third element: \{2\}, \{2, 5\}

contiguous subsequences starting from the fourth element: \{5\}

(Note that even if the elements of subsequences are equal, subsequences that have different starting indices are considered to be different.)

The maximum possible bitwise AND of the beauties of two different contiguous subsequences is 12.
This can be achieved by choosing \{5, 2, 5\} (with beauty 12) and \{2, 5, 2, 5\} (with beauty 14).

Sample Input 2

8 4
9 1 8 2 7 5 6 4

Sample Output 2

32

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)


import java.io.IOException;
import java.io.InputStream;
import java.util.*;
import java.util.List;


public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner();
        final int N=scanner.nextInt();
        final int k=scanner.nextInt();
        long[] a=new long[N];
        for(int i=0;i<N;i++){
            a[i]=scanner.nextInt();
        }
        long[] aa=new long[N+1];
        aa[0]=0;
        for(int i=1;i<N+1;i++){
            aa[i]=aa[i-1]+a[i-1];
        }
        List<Long> aaList=new ArrayList<>();
        for(int i=1;i<N+1;i++){
            for(int j=0;j<i;j++){
                aaList.add(aa[i]-aa[j]);
            }
        }
        Collections.sort(aaList,Comparator.reverseOrder());
        long result=aaList.get(0);
        for(int i=1;i<k;i++){
            result&=aaList.get(i);
        }
        put(result);

    }


    public static int upper_bound(int[] a,int val){
        return upper_bound(a,0,a.length,val);
    }
    public static int upper_bound(int[] a,int l,int r,int val){
        if(r-l==1){
            if(a[l]>val) return l;
            return r;
        }
        int mid=(l+r)/2;
        if(a[mid]>val){
            return upper_bound(a,l,mid,val);
        }else{
            return upper_bound(a,mid,r,val);
        }
    }
    public static int lower_bound(int[] a,int val){
        return lower_bound(a,0,a.length,val);
    }
    public static int lower_bound(int[] a,int l,int r,int val){
        if(r-l==1){
            if(a[l]<val) return r;
            return l;
        }
        int mid=(l+r)/2;
        if(a[mid]<val){
            return lower_bound(a,mid,r,val);
        }else{
            return lower_bound(a,l,mid,val);
        }

    }


    public static int max(int a,int b){
        return Math.max(a,b);
    }
    public static long max(long a,long b){
        return Math.max(a,b);
    }
    public static int min(int a,int b){
        return Math.min(a,b);
    }
    public static long min(long a,long b){
        return Math.min(a,b);
    }
    public static int abs(int a){
        return Math.abs(a);
    }
    public static long abs(long a){
        return Math.abs(a);
    }
    public static void print(Object object){
        System.out.print(object);
    }
    public static void put(Object object) {
        System.out.println(object);
    }
    public static void put(){
        System.out.println();
    }
    public static String format(String string, Object... args) {
        return String.format(string, args);
    }
}

final class Scanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;

    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        } else {
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }

    private int readByte() {
        if (hasNextByte())
            return buffer[ptr++];
        else
            return -1;
    }

    private boolean isPrintableChar(int c) {
        return 33 <= c && c <= 126;
    }

    public boolean hasNext() {
        while (hasNextByte() && !isPrintableChar(buffer[ptr]))
            ptr++;
        return hasNextByte();
    }

    public String next() {
        if (!hasNext())
            throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while (isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    public long nextLong() {
        if (!hasNext())
            throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while (true) {
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            } else if (b == -1 || !isPrintableChar(b)) {
                return minus ? -n : n;
            } else {
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }

    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
            throw new NumberFormatException();
        return (int) nl;
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }
}
final class FixedPair {
    final private int x, y;
    final static public FixedPair ZEROS=new FixedPair(0,0);
    FixedPair(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    @Override
    public int hashCode() {
        return x+y;
    }

    @Override
    public boolean equals(Object obj) {
        boolean result=super.equals(obj);
        if(obj.getClass()!=this.getClass()){
            return false;
        }
        FixedPair pair=(FixedPair)obj;
        if(this.x==pair.x&&this.y==pair.y) return true;
        return false;
    }

    @Override
    public String toString() {
        return String.format("(%d,%d)", x, y);
    }
}
final class Tuple<T,V>{
    //immutabl1でないことに注意(T,Vがmutableの場合変更可能)
    final private T t;
    final private V v;
    Tuple(T t,V v){
        this.t=t;
        this.v=v;
    }

    public T getT() {
        return t;
    }

    public V getV() {
        return v;
    }

    @Override
    public int hashCode() {
        return (t.hashCode()+v.hashCode());
    }

    @Override
    @SuppressWarnings("unchecked")
    public boolean equals(Object obj) {
        if(obj.getClass()!=this.getClass()){
            return false;
        }
        Tuple<T,V> tuple=(Tuple<T, V>) obj;
        return tuple.t.equals(this.t)&&tuple.v.equals(this.v);
    }

    @Override
    public String toString() {
        return String.format("<Tuple>=<%s,%s>",t,v);
    }
}
final class LowerBoundComparator<T extends Comparable<? super T>>
        implements Comparator<T>
{
    public int compare(T x, T y)
    {
        return (x.compareTo(y) >= 0) ? 1 : -1;
    }
}

final class UpperBoundComparator<T extends Comparable<? super T>>
        implements Comparator<T>
{
    public int compare(T x, T y)
    {
        return (x.compareTo(y) > 0) ? 1 : -1;
    }
}
final class Util {
    static long gcd(long a,long b){
        if(a%b==0)return b;
        return gcd(b,a%b);
    }
    static long lcm(long a,long b){
        long gcd=gcd(a,b);
        long result=b/gcd;
        return a*result;
    }
    static long kaijoMod(int n,int mod){
        if(n<1) return -1;
        long result=1;
        for(int i=n;i>1;i--){
            result*=i;
            result%=mod;
        }
        return result;
    }
    static <T extends Comparable<T>> Map<T,Integer> count(List<T> list){
        //副作用
        Collections.sort(list);
        Map<T,Integer> result=new HashMap<>();
        int l=0,r=0;
        while(l<list.size()){
            while(r<list.size()-1&&list.get(r).equals(r+1)){
                r++;
            }
            result.put(list.get(r),r-l+1);
            r++;
            l=r;
        }
        return result;

    }
    static Map<Integer,Integer> count(int[] array){
        //副作用
        Arrays.sort(array);
        Map<Integer,Integer> result=new HashMap<>();
        int l=0,r=0;
        while(l<array.length){
            while(r<array.length-1&&array[r]==array[r+1]){
                r++;
            }
            result.put(array[l],r-l+1);
            r++;
            l=r;
        }
        return result;
    }
    static <T> String toStringBWS(Iterable<T> iterable){
        Iterator<T> ite=iterable.iterator();
        return toStringBWS(ite);
    }
    static <T> String toStringBWS(Iterator<T> ite){
        StringBuilder sb=new StringBuilder();
        sb.append(ite.next());
        while(ite.hasNext()){
            sb.append(" ");
            sb.append(ite.next());
        }
        return sb.toString();
    }
    static String toStringBWS(int[] array){
        StringBuilder sb=new StringBuilder();
        for(int i=0;i<array.length-1;i++){
            sb.append(array[i]);
            sb.append(" ");
        }
        sb.append(array[array.length-1]);
        return sb.toString();
    }
    static String toStringBWS(long[] array){
        StringBuilder sb=new StringBuilder();
        for(int i=0;i<array.length-1;i++){
            sb.append(array[i]);
            sb.append(" ");
        }
        sb.append(array[array.length-1]);
        return sb.toString();
    }
}