import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int K = scan.nextInt();
		long[]a = new long[N];
		for(int i = 0; i < N; i++) {
			a[i] = scan.nextLong();
		}
		scan.close();
		Arrays.sort(a);
		long[]d = new long[N - 1];
		for(int i = 0; i < N - 1; i++) {
			d[i] = a[i + 1] - a[i];
		}
		Arrays.sort(d);
		long ans = 0;
		for(int i = 0; i < N - K; i++) {
			ans += d[i];
		}
		System.out.println(ans);
	}
}