#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long LL;
int main(int argc, char* argv[])
{
	int N,K;
	cin>>N>>K;
	vector<LL> A(N),B(N-1);
	int i;
	for (i=0;i<N;i++){
		cin>>A[i];
	}
	if (N==1){
		cout<<0;
		return 0;
	}
	sort(A.begin(),A.end());
	for (i=1;i<N;i++){
		B[i-1]=A[i]-A[i-1];
	}
	sort(B.begin(),B.end());
	LL ans=0;
	for (i=0;i<N-K;i++){
		ans+=B[i];
	}
	cout<<ans<<endl;
	return 0;
}