import java.util.*;
import java.io.*;
import java.text.*;
class p{
    static final long MOD = (long)1e9+7;
    static int L = 16;
    static final int MAX = (int)5e4+50;
    static FastReader in;
    
    static int N, ptr;
    static Node[] trie;
    static int[] A, xor, rt;
    static long K, cur;
    public static void main(String[] args){
        in = new FastReader();
        
        A = new int[MAX];
        xor = new int[MAX];
        rt = new int[MAX];
        trie = new Node[MAX*(L+1)];
        for(int i = 0; i< trie.length; i++)trie[i] = new Node();
        rt[0] = insert(0, 0);
        N = ni(); K = nl();
        for(int i = 1; i<= N; i++){
            A[i] = ni();
            xor[i] = xor[i-1]^A[i];
            rt[i] = insert(rt[i-1], xor[i]);
        }
        long lo = 0, hi = N*(1<<L);
        long ans = 0;
        while(lo <= hi){
            long mid = (lo+hi)>>1;
            cur = 0;
            count(1, N, mid);
            if(cur>=K){
                hi = mid-1;
                ans = mid;
            }else lo = mid+1;
        }
        pn(ans);
    }
    
    static void count(int l, int r, long mid){
        if(r<l || cur>=K)return;
        if(l==r){
            if(A[l]*(long)A[l] <= mid)cur++;
            return;
        }
        int p = 0;
        long min = Long.MAX_VALUE;
        for(int i = l; i<= r; i++){
            if(A[i]<min){
                min = A[i];
                p = i;
            }
        }
        count(l, p-1, mid);
        count(p+1, r, mid);
        if(cur>=K)return;
        long x = mid/A[p];
        if(p-l <= r-p){
            for(int i = l; i<= p; i++)cur += get(rt[r], xor[i-1], x) - get(rt[p-1], xor[i-1], x);
        }else{
            for(int i = p; i<= r; i++)cur += get(rt[p-1], xor[i], x) - ((l>=2)?get(rt[l-2], xor[i], x):0);
        }
    }
    
    static int insert(int prev, int x){
        int root = ++ptr, ret = root;
        trie[root] = new Node(trie[prev].count+1, trie[prev].to[0], trie[prev].to[1]);
        for(int i = L-1; i>= 0; i--){
            int bit = (x>>i)&1, nxt = ++ptr;
            if(trie[root].to[bit] != -1){
                trie[nxt] = new Node(trie[trie[root].to[bit]].count, trie[trie[root].to[bit]].to[0], trie[trie[root].to[bit]].to[1]);
            }
            trie[root].to[bit] = nxt;
            root = nxt;
            trie[root].count++;
        }
        return ret;
    }
    
    static long get(int root, int xo, long x){
        long out = 0, nw = 0;
        for(int i = L-1; i>= 0; i--){
            if(root == -1)break;
            int bit = (xo>>i)&1;
            if((nw|(1<<i)) <= x){
                int z = trie[root].to[bit];
                if(z!=-1)out+=trie[z].count;
                root = trie[root].to[bit^1];
                nw|=1<<i;
            }else root = trie[root].to[bit];
        }
        if(nw <= x && root !=-1)out += trie[root].count;
        return out;
    }
    
    static class Node{
        int count = 0;
        int[] to;
        public Node(){
            count = 0;
            to = new int[]{-1, -1};
        }
        
        public Node(int c){
            count = c;
            to = new int[]{-1, -1};
        }
        
        public Node(int c, int t1, int t2){
            count = c;
            to = new int[]{t1, t2};
        }
    }
    
    static void p(Object o){
        System.out.print(o);
    }
    
    static void pn(Object o){
        System.out.println(o);
    }
    
    static String n(){
        return in.next();
    }
    
    static String nln(){
        return in.nextLine();
    }
    
    static int ni(){
            return Integer.parseInt(in.next());
    }
    
    static long nl(){
        return Long.parseLong(in.next());
    }
    
    static double nd(){
        return Double.parseDouble(in.next());
    }
    
    static class FastReader{
        BufferedReader br;
        StringTokenizer st;
        public FastReader(){
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        
        public FastReader(String s) throws Exception{
            br = new BufferedReader(new FileReader(s));
        }
 
        String next(){
            while (st == null || !st.hasMoreElements()){
                try{
                    st = new StringTokenizer(br.readLine());
                }catch (IOException  e){
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        String nextLine(){
            String str = "";
            try{
                str = br.readLine();
            }catch (IOException e){
                e.printStackTrace();
            }
            return str;
        }
    }
}