Merge Sort Program

#include<iostream.h>
#include<conio.h>
#include<values.h>
void merge(int a[],int p,int q,int r)
{
 int n1=q-p+1,n2=r-q;
 int *l=new int[n1+1];
 int *rt=new int[n2+1];
 for(int i=0;i<n1;i++)
       l[i]=a[p+i];

 for(int j=0;j<n2;j++)
  rt[j]=a[q+j+1];  
 l[n1]=MAXINT;   //SENTINEL
 rt[n2]=MAXINT;  //SENTINEL
 i=j=0;
 for(int k=p;k<=r;k++)
 {
  if(l[i]<=rt[j])
  {
   a[k]=l[i];
   i+=1;
  }
  else
  {
   a[k]=rt[j];
   j+=1;
  }
 }
}
void mergesort(int a[],int p,int r)
{
 int q;
 if(p<r)
 {
  q=(p+r)/2;
  mergesort(a,p,q);
  mergesort(a,q+1,r);
  merge(a,p,q,r);
 }
}
void main()
{
 clrscr();
 int n;
 cout<<"\nEnter the no. of elements you want:";
 cin>>n;
 int *a=new int[n];  //dynamically initialize array
 cout<<"\nEnter the elements:\n";
 for(int i=0;i<n;i++)
  cin>>a[i];

 mergesort(a,0,n-1);
 cout<<"\n\nSORTED ARRAY IS:\n";
 for( i=0;i<n;i++)
  cout<<a[i]<<" ";
 getch();
}