source_code: import java.io.*;
  import java.util.*;
  
  import javax.lang.model.util.ElementScanner6;
  public class codef
  {
      public static void main(String ar[]) throws IOException
      {
          BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer nk=new StringTokenizer(br.readLine());
          int n=Integer.parseInt(nk.nextToken());
          int k=Integer.parseInt(nk.nextToken());
          String st[]=br.readLine().split(" ");
          
          int ans[]=new int[n];
          int a[]=new int[n];
          for(int i=0;i<n;i++)
              ans[i]=Integer.parseInt(st[i]);  
  
          for(int i=1;i<n;i++)
              a[i]=ans[i]-ans[i-1];
          a[0]=-1;
  
          Arrays.sort(a);
          int count=0,sum=0;
          for(int i=0;i<n;i++)
              if(a[i]<0)
                  count++;
              else
                  sum=sum+a[i];
          
          k=k-count;
          int i=n-1;
          while(k>0 && i>=0)
          {
              if(a[i]>-1)
              {
                  sum=sum-a[i];
                  k--;
              }
              i--;
          }
          System.out.println(sum);
      }
  }