#include<iostream>

#include<cstring>

#include<cstdio>

#include<queue>

#include<cmath>

#include<algorithm>

using namespace std;

typedef long long ll;

const int N=5e5+;

int n,k,cnt;

int rt[N];

ll a[N];

struct Trie

{

    int ch[];

    int id,siz;

}t[N*];

inline ll read()

{

    char ch=getchar();ll s=,f=;

    while (ch<''||ch>'') {if (ch=='-') f=-;ch=getchar();}

    while (ch>=''&&ch<='') {s=(s<<)+(s<<)+ch-'';ch=getchar();}

    return s*f;

}

void ins(int &now,int pre,int bit,int id,ll val)

{

    now=++cnt;t[now]=t[pre];t[now].siz++;

    if (bit==-)

    {

        t[now].id=id;

        return;

    }

    if ((val>>bit)&) ins(t[now].ch[],t[pre].ch[],bit-,id,val);

    else ins(t[now].ch[],t[pre].ch[],bit-,id,val);

}

int query(int k1,int k2,int bit,ll val)

{

    if (bit==-) return t[k2].id;

    int d=(val>>bit)&;

    if (t[t[k2].ch[d^]].siz-t[t[k1].ch[d^]].siz>) return query(t[k1].ch[d^],t[k2].ch[d^],bit-,val);

    return query(t[k1].ch[d],t[k2].ch[d],bit-,val);

}

struct node

{

    int l,r,x,id;ll val;

    node(int _l=,int _r=,int _x=)

    {

        l=_l;r=_r;x=_x;

        id=query(rt[l-],rt[r],,a[x]);

        val=a[x]^a[id-];

    }

};

bool operator < (const node &a,const node &b) {return a.val<b.val;}

priority_queue<node> Q;

int main()

{

    freopen("xor.in","r",stdin);

    freopen("xor.out","w",stdout);

    n=read();k=read();

    for (int i=;i<=n;i++) a[i]=a[i-]^read();

    for (int i=;i<=n;i++) ins(rt[i],rt[i-],,i,a[i-]);

    for (int i=;i<=n;i++) Q.push(node(,i,i));

    ll ans=;

    while (k--)

    {

        node u=Q.top();Q.pop();

        ans+=u.val;

        if (u.l<u.id) Q.push(node(u.l,u.id-,u.x));

        if (u.r>u.id) Q.push(node(u.id+,u.r,u.x));

    }

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

    return ;

}