I'm very often have ACCESS_VIOLATION.
For example, in task 1079 http://acm.timus.ru/messages.asp?id=4539

And in this too. Why??

#include <iostream.h>

int begin [10000], end [10000];


void sort (int l,int r)
{
    int  i,j,x,y;
    i=l; j=r; x=end[(l+r) / 2];
  do
  {
    while (end[i]<x) i++;
    while (x<end[j]) j--;
    if (i<=j)
    {
      y=end[i]; end[i]=end[j]; end[j]=y;
      y=begin[i]; begin[i]=begin[j]; begin[j]=y;
      i++; j--;
    }
  } while (i<j);
  if (l<j) sort(l,j);
  if (i<r) sort(i,r);
}

void quicksort (int Lo,int Hi)
{
    sort(Lo,Hi);
}



int main ()
{
    long n;
    cin >> n;
    for (long i=1; i<=n; i++) cin >> begin [i] >> end [i];
    int last=1,now=1,all=1;
    quicksort (1,n);
    while (now<n)
    {
    while (begin [++now] <= end [last])
        if (n == now)
        {
            all--;
            break;
        }
    last = now;
    all++;
    }
    cout << all;
    return 0;
}