#include <cmath>

#include <cstring>

#include <cstdlib>

#include <iostream>

#include <algorithm>

#include <queue>

#include <stack>

#define ll long long

using namespace std;

struct Trie

{

    int to[];

    int ed;

}tree[];

struct node

{

    ll v;

    int rq;

    int num;

    friend bool operator < (node a,node b)

    {

        return a.v<b.v;

    }

};

priority_queue <node> M;

int rt[];

ll a[];

int n,k;

int tot=;

void ins(ll x,int now,int las)

{

    rt[now]=++tot;

    now=rt[now],las=rt[las];

    for(int i=;i>=;i--)

    {

        tree[now]=tree[las];

        tree[now].ed++;

        if((x>>i)&)tree[now].to[]=++tot,now=tree[now].to[],las=tree[las].to[];

        else tree[now].to[]=++tot,now=tree[now].to[],las=tree[las].to[];

    }

    tree[now].ed=tree[las].ed+;

}

ll query(int lq,int rq,ll x,int rk,int temp)

{

    if(temp==-)return ;

    int t=((x>>temp)&)?:;

    int sum=tree[tree[rq].to[t]].ed-tree[tree[lq].to[t]].ed;

    if(sum>=rk)return query(tree[lq].to[t],tree[rq].to[t],x,rk,temp-)+(1ll<<temp);

    else return query(tree[lq].to[t^],tree[rq].to[t^],x,rk-sum,temp-);

}

int main()

{

    scanf("%d%d",&n,&k);

    n++;

    ins(,,);

    for(int i=;i<=n;i++)scanf("%lld",&a[i]),a[i]^=a[i-],ins(a[i],i,i-);

    for(int i=;i<=n;i++)M.push((node){query(rt[],rt[i],a[i],,),i,});

    ll ans=;

    for(int i=;i<=k;i++)

    {

        node temp=M.top();

        M.pop();

        ans+=1ll*temp.v;

        if(temp.num<temp.rq)M.push((node){query(rt[],rt[temp.rq],a[temp.rq],temp.num+,),temp.rq,temp.num+});

    }

    printf("%lld\n",ans);

    return ;

}