#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <math.h>

using namespace std;

#define REP(i,n)	for(int i=0;i<(n);++i)
#define REPS(i,s,t)	for(int i=(s);i<(t);++i)

#define INF 		2000000007
#define MOD			1000000007
#define MAX 		100005


typedef unsigned int 			uint;
typedef unsigned long long int	ull;
typedef long long int ll;

//uint dp[MAX];

int main(){
	int N,K;cin>>N>>K;
	vector<ull> A(N);
	REP(i,N)cin>>A[i];

	sort(A.begin(),A.end());
	vector<ull> diff(N-1);
	REP(i,N-1){
		diff[i] = A[i+1] - A[i];
	}
	sort(diff.begin(),diff.end());
	ull ans = 0;
	REP(i,N-K)ans += diff[i];

	cout << ans << endl;


	return 0;
}