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

int main(void)
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int N, K;
	cin >> N >> K;

	vector<int> v(N);

	for (int i = 0; i < N; i++)
	{
		cin >> v[i];
	}
	
	// 예외 처리
	if (K >= N)
	{
		cout << "0";

		return 0;
	}

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

	vector<int> diff(N - 1);

	for (int i = 0; i < N - 1; i++)
	{
		diff[i] = v[i + 1] - v[i];
	}

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

	int result = 0;

	for (int i = 0; i < N - K; i++)
	{
		result += diff[i];
	}

	cout << result << "\n";

	return 0;
}