#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <sstream>
#include<set>
#include<stack>

//#include<bits/stdc++.h>


using namespace std;



int main() {
	
	int n,m;
	cin >> n >> m;

	vector<long long int>p(n);

	for (int i = 0; i < n; i++)cin >> p[i];
	sort(p.begin(), p.end());

	vector<pair<long long int, int>>r;
	for (int i = 0; i < n - 1; i++) {
		r.push_back(make_pair(p[i+1]-p[i],i));
	}
	sort(r.rbegin(), r.rend());
	vector < bool>f(n);
	for (int i = 0; i < m - 1; i++)f[r[i].second] = 1;
	long long int ans = 0;
	vector<long long int>w;
	for (int i = 0; i < n ; i++) {
		w.push_back(p[i]);
		if (f[i]) {
			sort(w.begin(), w.end());
			ans += w[w.size() - 1] - w[0];
			w.clear();
		}

	}
	sort(w.begin(), w.end());
	ans += w[w.size() - 1] - w[0];
	w.clear();

	cout << ans << endl;

	return 0;


		
}