#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cstdio>

using namespace std;

int n,k,a[100001];

int cmp(const void *a,const void *b)
{
	return (*(int *)a)-(*(int *)b);
}

int main()
{
	freopen("chess.in","r",stdin);
	freopen("chess.out","w",stdout);
	scanf("%d%d",&n,&k);
	for (int i=1;i<=n;i++)
	scanf("%d",&a[i]);
	qsort(a+1,n,sizeof(a[0]),cmp);
	for (int i=n;i>1;i--) a[i]-=a[i-1];
	qsort(a+2,n-1,sizeof(a[0]),cmp);
	int ans=0;
	for (int i=2;i<=k+1;i++)
	ans+=a[i];
	printf("%d\n",ans);
	return 0;
}