#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
using namespace std;
typedef long long int ll;
const int S = 50000;
ll a[S],n,k,dif[S];
int main() {
	cin >> n >> k;
	for (int i = 0; i < n; i++)cin >> a[i];
	sort(a, a + n);
	for (int i = 0; i < n - 1; i++)dif[i] = a[i + 1] - a[i];
	sort(dif, dif + n - 1);
	ll d_tot = 0;
	for (int i = 0; i < k - 1; i++)d_tot += dif[n-2-i];
	cout << a[n - 1] - a[0] - d_tot << endl;
	return 0;
}