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[] dif = new long[n - 1];
    	for (int i = 0; i < n - 1; i++) {
    	    dif[i] = arr[i + 1] - arr[i];
    	}
    	Arrays.sort(dif);
    	long ans = 0;
    	for (int i = 0; i < n - k; i++) {
    	    ans += dif[i];
    	}
    	System.out.println(ans);
	}
}