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

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