//P3620 [APIO/CTSC 2007] 数据备份
//把每组相邻城市的距离作为点 则题意转化为n-1中选取k个点
//使总和最小且这些点互不相邻;反悔策略：用选取的点相邻两点之和减去该点点权作为返回策略 
#include<bits/stdc++.h>
using namespace std;
#define ll long long 
#define inf 0x3f3f3f
const int nn=500010;
inline ll read(){
	ll w=1,s=0;char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-1')w=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return w*s;
}
struct node{
	ll v,id;
	bool operator < (const node &xs) const{
		return v>xs.v;
	}
}t,s,f;
struct nd{
	ll v,l,r;
}p[nn];
inline void del(int x)
{
	p[x].l=p[p[x].l].l;
	p[x].r=p[p[x].r].r;
	p[p[x].l].r=x;
	p[p[x].r].l=x;
}
ll k,qwq,n,m,l,qaq;
bool vis[nn];
priority_queue<node> q;
void init(node a){cout<<a.id<<" "<<a.v<<endl;}
int main(){
	n=read();m=read();l=read();
 	for(int i=1;i<n;i++){
 		qwq=read();
 		p[i].v=qwq-l;l=qwq;
 		p[i].l=i-1;p[i].r=i+1;
 		s.id=i;s.v=p[i].v;
		 q.push(s);
//		 cout<<s.id<<" ";
	 }
	 p[0].v=p[n].v=inf;
 	for(int i=1;i<=m;++i){
 		while(vis[q.top().id])
		 q.pop();
		 
		 t=q.top();q.pop();
 			qaq+=t.v;
			 vis[p[t.id].l]=vis[p[t.id].r]=1;
			 p[t.id].v=p[p[t.id].l].v+p[p[t.id].r].v-p[t.id].v;
			 f.v=p[t.id].v;f.id=t.id;
			 q.push(f);
//			 init(t);
			 del(f.id);
//		 cout<<t.id<<" "<<t.v<<endl;
	 }
	 cout<<qaq;
	 return 0;
}

输出203998411 正解537092323 不太理解哪里错了求大佬指教