#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <stdio.h>
#include <cstring>
#include <queue>
#include <stack>
#include <functional>
#include <math.h>
#include <iomanip>
using namespace std;
#define Would
#define you
const int INF = 999999999;
const int MOD = 1e9 + 7;
const double pi = 3.141592653589793238;

int main() {
	int a, b;
	long long k[50005], l[50005], ans = 0;
	cin >> a >> b;
	for (int i = 0; i < a; ++i) { cin >> k[i]; }
	sort(k, k + a);
	for (int i = 1; i < a; ++i) {
		l[i] = k[i] - k[i - 1];
	}
	sort(l, l + a - 1);
	for (int i = 0; i < a - b; ++i) {
		ans += l[i];
	}
	cout << ans << endl;
}