#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	int N, K;
	long a[50000], ans = 0, tmp[49999];
	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) tmp[i] = a[i + 1] - a[i];
	sort(tmp, tmp + N - 1);
	for (int i = 0; i < N - K; ++i) ans += tmp[i];
	cout << ans;
}