#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
using namespace std;
const int maxn = 100010;
int num[maxn],tmp[maxn];
int N,K,Ans;


bool cmp(const int a,const int b)
{
	return a < b;
}


void prep()
{
	scanf("%d%d",&N,&K);
	for (int i=1; i<=N; i++) scanf("%d",&num[i]);
	sort(num+1,num+1+N,cmp);
}

void work()
{
	for (int i=1; i<N; i++) tmp[i] = num[i+1] - num[i];
	sort(tmp+1,tmp+1+N-1,cmp);
	for (int i=1; i<=K; i++) Ans += tmp[i];
	printf("%d\n",Ans);
}

int main()
{
	freopen("chess.in","r",stdin);
	freopen("chess.out","w",stdout);
	prep();
	work();
	return 0;
}