#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main(void) {
	int n, k;
	cin >> n >> k;
	vector<long long> a(n);
	for (int i = 0; i < n; ++i) cin >> a[i];
	sort(a.begin(), a.end());
	vector<long long> diff(n - 1);
	for (int i = 0; i < n - 1; ++i)
		diff[i] = a[i + 1] - a[i];
	sort(diff.begin(), diff.end());
	long long sum = 0;
	for (int i = 0; i < n - k; ++i) {
		sum += diff[i];
	}
	cout << sum << endl;
	return 0;
}