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

	return 0;
}