求助 0 pts

#include<bits/stdc++.h>
using namespace std;

#define L(i,j,k) for(int i=j;i<=k;i++)
#define ll long long

const int N=2e7+1000;

int n,k;
ll number[N];

int t[N];



int ch[N][2];
int siz[N],tot;

void insert(ll x){
	int u=0;
	for(ll i=31;i>=0;i--){
		int op=(x>>i)&1;
		siz[u]++;
		if(!ch[u][op])ch[u][op]=++tot;
		u=ch[u][op];
	}
	siz[u]++;
}

ll query(ll x,int rk){
	int u=0;ll ans=0;
	for(int i=31;i>=0;i--){
		int op=(x>>i)&1;
		if(!ch[u][op^1])u=ch[u][op];
		else if(rk<=siz[ch[u][op^1]])u=ch[u][op^1],ans|=(1ll<<i);
		else rk-=siz[ch[u][op^1]],u=ch[u][op];
	}
	return ans;
}

#define mp make_pair
#define pr pair<ll,int>
priority_queue< pr > Queue;

ll ans;

int main(){
	
#ifndef ONLINE_JUDGE
	freopen("in.in","r",stdin);
#endif
	
//	ios::sync_with_stdio(0);
	
	
	cin>>n>>k;k*=2;
	
	L(i,1,n){
		cin>>number[i];
		number[i]^=number[i-1];
	}
	
	L(i,0,n)t[i]=1;
	L(i,0,n)insert(number[i]);
	L(i,0,n)Queue.push(mp(query(number[i],1),i));
	L(i,1,k){
		auto x=Queue.top();ans+=x.first;Queue.pop();
		if(t[x.second]<n){
			t[x.second]++;
			Queue.push(mp(query(number[i],t[x.second]),x.second));
		}
	}
	cout<<ans/2<<'\n';
	
	
	return 0;
}