#include <bits/stdc++.h>
using namespace std;

int main() {
	int64_t n, k;
	cin >> n >> k;
	int64_t a[n];
	for (auto &i : a) {
		cin >> i;
	}
	if (n == 1) {
		cout << 0 << endl;
		return 0;
	}
	sort(a, a + n);
	int64_t b[n - 1];
	for (int i = 0; i < n - 1; i++) {
		b[i] = a[i + 1] - a[i];
	}
	sort(b, b + n - 1);
	int64_t ans = 0;
	for (int i = 0; i < n - k; i++) {
		ans += b[i];
	}
	cout << ans << endl;
	return 0;
}