import java.util.*;

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