#include<bits/stdc++.h>
using namespace std;
int n,k,ans;
const int N=1000005;
int come[N],none[N];
int main ()
{
	scanf("%d%d",&n,&k);
	for(int i=1;i<=n;i++){
		scanf("%d",come+i);
	}
	ans+=come[n]+1-come[1];
	for(int i=1;i<n;i++){
		none[i]=come[i+1]-1-come[1];
	}
	sort(none+1,none+n);
	for(int i=n-1;i>=n-k+1;i--){
		ans-=none[i];
	}
	printf("%d",ans);
	return 0;
}

谢谢！