C++ :

#include <iostream>
#include <algorithm>
#include <set>
using namespace std;
typedef long long LL;
typedef pair<LL,int> PLI;
const int N=1e5+5;

int n,k;
int l[N],r[N];
LL d[N];

void delete_node(int x){
	r[l[x]]=r[x];
	l[r[x]]=l[x];
}

int main()
{
	ios::sync_with_stdio(false);
	cin>>n>>k;
	for(int i=0;i<n;i++) cin>>d[i];
	for(int i=n-1;i;i--) d[i]-=d[i-1];
	
	set<PLI> s;
	d[0] = d[n] = 1e15;
	for(int i=0;i<=n;i++) {
		s.insert({d[i],i});
		l[i]=i-1;
		r[i]=i+1;
	}
	
	LL ans=0;
	while(k--){
		auto x=s.begin();
		LL v=x->first;
		int p=x->second,left=l[p],right=r[p];
		
		ans+=v;
		
		s.erase(x);
		s.erase({d[left],left});
		s.erase({d[right],right});
		delete_node(left);
		delete_node(right);
		
		d[p]=d[left]+d[right]-d[p];
		s.insert({d[p],p});
	}
	cout<<ans<<endl;
	return 0;
}