How to optimise this C code..

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

void quicksort(long int [100000],long int,long int);

int main()
{
  long int packs[100000],n,k,i,j;
  long int key1=0,key2 = 999999999;
  long int temp = 999999999 ;
  long int l;

  scanf("%ld",&n);
  scanf("%ld",&k);

  for(i=0;i<n;i++)
    scanf("%ld",&packs[i]);
    // packs[i] = random(1000000);

     quicksort(packs,0,n-1);

  for(i=0;i<(n-k);i++)
   {
    for(j=i;j<(k-1+i);j++)
     {
       for(l=j+1;l<=(k-1+i);l++)
       {

     //     if(key2>key1)
       key1 += abs(packs[j]-packs[l]);
       //else
        //continue;
       }
     }
   if( key1 < temp)
    key2 = temp = key1;
      key1 = 0;
      }


printf("%ld",temp);

     return 0;
}

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

void quicksort(long int [100000],long int,long int);

long int main()
{
  long int packs[100000],n,k,i,j;
  long int key1 = 0,key2 = 0;
  long int temp = 0 ;
  long int l,m;

  scanf("%ld",&n);
  scanf("%ld",&k);

  for(i=0;i<n;i++)
   // scanf("%lld",&packs[i]);
    packs[i] = random(1000000);

     quicksort(packs,0,n-1);


  for(l=0;l<k;l++)
   for(m=l;m<k;m++)
  {
   key1 = temp += abs(packs[l] - packs[m]);
  }
//printf("\n\n%ld\n\n",temp);

  for(i=1;i<(n-k);i++)
   {
    for(j=i;j<(k+i-1);j++)
     {
     key1 += abs(packs[j] - packs[k+i-1]);
     key2 += abs(packs[j] - packs[i-1]);
     }
     key1 = key1-key2 ;
   if( key1 < temp)
    temp = key1;
      key2 = 0;
	 // printf("\n\n%ld",key1);
	  }


printf("%ld",temp);

     return 0;
}