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

public class No615 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int K = sc.nextInt();
		
		if(N == K) {
			System.out.println(0);
		}else {
			long a[] = new long[N];
			for(int i = 0;i < N;i++) {
				a[i] = sc.nextLong();
			}
			Arrays.sort(a);
			if(K == 1) {
				System.out.println(a[N-1] - a[0]);
			}else {
			
				int b[] = new int[K-1]; //分割する位置を入れる配列(a[i] a[i+1]の間で分割するならiが入る)
				long max[] = new long[K-1];
				long sum = 0;
				for(int i = 0;i < K-1;i++) {
					max[i] = 0;
				}
				for(int i = 0;i < N-1;i++) {
					if(max[0] < a[i+1] - a[i]) {
						max[0] = a[i+1] - a[i];
						b[0] = i;
						Arrays.sort(max);
						Arrays.sort(b);
					}
				}
				
				for(int i = 0;i < K-1;i++) {
					if(i == 0) {
						sum += a[b[i]] - a[0];
					}else {
						sum += a[b[i]] - a[b[i-1]+1];
					}
					if(i + 1 == K - 1) {
						sum += a[N-1] - a[b[i]+1];
					}
				}
				
				System.out.println(sum);
			}
		}
	}
}