import java.util.*;
import java.util.stream.*;

class A{
	public static void main(String[] $){
		Scanner s=new Scanner(System.in);
		int n=s.nextInt(),k=s.nextInt();
		long[]a=LongStream.range(0,n).map(i->s.nextLong())
				.sorted()
				.toArray();
		long init=a[n-1]-a[0];
		for(int i=n-1;i>0;--i)
			a[i]-=a[i-1];
		a[0]=0;
		System.out.println(
				init
				-Arrays.stream(a)
				.sorted()
				.skip(n-k+1)
				.sum()
				);
	}
}