#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ul = unsigned long;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	int n, k;
	cin >> n >> k;

	vector<ll> a(n);
	for (auto&& ia : a)
		cin >> ia;

	sort(a.begin(), a.end());

	vector<ll> d(n);
	adjacent_difference(a.begin(), a.end(), d.begin());
	sort(d.begin() + 1, d.end());

	ll res{ 0 };
	for (int i = 1; i <= n - k; ++i)
		res += d[i];
	cout << res << "\n";

	return 0;
}