Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<queue>

#include<cstring>

using namespace std;

int n,m;

#define MAXN 200010

int val[MAXN];

int lef[MAXN],rig[MAXN];

#define fi first

#define se second

bool v[MAXN];

int main()

{

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

	if(m * 2 > n)

	{

		puts("Error!");

		return 0;

	}

	for(int i = 1;i <= n;++i)scanf("%d",&val[i]);

	for(int i = 1;i <= n;++i)

	{

		lef[i] = i - 1;rig[i] = i + 1;

	}

	lef[1] = n;rig[n] = 1;

	priority_queue< pair<int,int> > q;

	for(int i = 1;i <= n;++i)

	{

		q.push(make_pair(val[i],i));

	}

	int ans = 0;

	memset(v,false,sizeof(v));

	for(int i = 1;i <= m;)

	{

		pair<int,int> k = q.top();q.pop();

		if(v[k.se])continue;

		ans += k.fi;++i;

		val[k.se] = val[lef[k.se]] + val[rig[k.se]] - val[k.se];

		v[lef[k.se]] = true;v[rig[k.se]] = true;

		rig[lef[lef[k.se]]] = k.se;lef[k.se] = lef[lef[k.se]];

		lef[rig[rig[k.se]]] = k.se;rig[k.se] = rig[rig[k.se]];

		q.push(make_pair(val[k.se],k.se));

	}

	cout << ans << endl;

	return 0;

}