import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		long[] arr = new long[n];
		for (int i = 0; i < n; i++) {
		    arr[i] = sc.nextLong();
		}
		Arrays.sort(arr);
		long total = 0;
		for (int i = 0; i < n - 1; i++) {
		    arr[i] = arr[i + 1] - arr[i];
		    total += arr[i];
		}
		arr[n - 1] = 0;
		Arrays.sort(arr);
		for (int i = 0; i < k - 1; i++) {
		    total -= arr[n - i - 1];
		}
		System.out.println(total);
	}
}