#include <iostream>
#include <cstdint>
#include <vector>
#include <algorithm>
#include <functional>

using namespace std;

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

	uint16_t N, K, i;
	cin >> N >> K;
	vector<uint64_t> a(N);
	for (i = 0; i != N; ++i) cin >> a[i];

	sort(a.begin(), a.end(), greater<uint64_t>());
	vector<uint64_t> gap(N - 1);
	for (i = 1; i != N; ++i) gap[i - 1] = a[i - 1] - a[i];

	sort(gap.begin(), gap.end(), greater<uint64_t>());
	uint64_t gap_sum = 0;
	for (i = 0; i != K - 1; ++i) gap_sum += gap[i];

	cout << a[0] - a[N - 1] - gap_sum << '\n';
	return 0;
}