#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <map>
#include <iomanip>
#include <math.h> 
#include <stack>
#include <queue>
#include <bitset>
#include <cstdlib>
#include <tuple>
#include <cctype>
#include <ctype.h>
#include <set>
#include <sstream>
#include <time.h>
using namespace std;
#define int long long
#define rep(i,s,n) for(int i = s;i<n;i++)
#define repe(i,s,n) for(int i = s;i<=n;i++)
#define rrep(i,s,n) for(int i = (n)-1;i>=(s);i--)
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define fi first
#define se second
#define chmin(a,b) a=min((a),(b))
#define chmax(a,b) a=max((a),(b))
#define l1 list[index]
#define l2 list[index - 1]
#define l3 list[index + 1]
#define iif(i,j) ((i<0 && j<0) || (i>0 && j>0)) ? true : false 
typedef long long ll;
typedef pair<int, int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
typedef pair<pint, int> P1;
typedef pair<int, pint> P2;
typedef pair<pint, pint> PP;
static const ll maxLL = (ll)1 << 62;
const ll MOD = 1000000007;
const ll INF = 1e18;
const double PI = 3.14159265359;
int ca[12] = { 31,28,31,30,31,30,31,31,30,31,30,31 };



signed main() {
	string s;
	//vector<vector<int>>list(200000, vector<int>(2));
	vector<int>listsum;
	vector<pair<int, int>>list, list2;
	int l, cnt = 0, maxn = 0;
	int n, n2, k, sum = 0, sumsum = 0;

	cin >> n >> k;

	listsum.push_back(0);

	for (int i = 0; i < n; i++) {
		int num;
		cin >> num;
		//list.push_back(num);
		list.push_back(make_pair( num, i));
		//sumsum += num;
	}
	//cout << endl;

	sort(list.begin(), list.end());
	sumsum = list[list.size() - 1].first - list[0].first;

	for (int i = 1; i < n; i++) {
		int num = list[i].first - list[i - 1].first;
		list2.push_back( make_pair(num, i - 1));
		//list2.push_back(num);
		listsum.push_back(listsum[listsum.size() - 1] + list[i].first);
	}

	sort(list2.begin(), list2.end());
	vector<int>list4;

	for (int i = 0; i < k-1; i++) {
		//list4.push_back(list2[list2.size() - i - 1].second);
		sumsum -= list2[list2.size() - i - 1].first;
	}

	//cout << "sumsum->" << sumsum << endl;
	cout << sumsum << endl;

	//sort(list4.begin(), list4.end());

	//int index = 0;

	//for (int i = 0; i < (int)list4.size(); i++) {
	//	//sum += listsum[list4[i]] - listsum[index];
	//	sum += list[list4[i]].first - list[index].first;
	//	index = list4[i] + 1;
	//}

	//cout << "sum->" << sum << endl;

	//for (int i = 0; i < n; i++) {
	//	cout << list[i].first << " ";
	//}
	//cout << endl;

	//for (int i = 0; i < (int)list2.size(); i++) {
	//	cout << list2[i].first << " ";
	//}
	//cout << endl;






	getchar();
	getchar();
	return 0;
}