Merge two sorted arrays a and b & store the final merged array a

Given two sorted arrays, of same size, merge them into single array and store the resultant array in a

For Example:

If the arrays are :
1 3 5 7 9
2 4 6 8 10

then the resultant merged array should be
1 2 3 4 5 6 7 8 9 10

Implementation:

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

int main(void) {
 int *a,*b,n,i,*temp,j,l,r,mid;
 
 /* Get the number of elements of the array */
 scanf("%d",&n);
 
 /* Dynamically allocate the memory block of n integers and store the address of a */
 a=(int*)malloc(sizeof(int)*n);
 
 /* Dynamically allocate the memory block of n integers and store the address of b */
 b=(int*)malloc(sizeof(int)*n);
 
 /* Dynamically allocate the memory block of 2*n integers and store the address of temp */
 temp=(int*)malloc(sizeof(int)*2*n);
 
 /* Get the elements of the array a */
 for(i=0;i<n;i++)
  scanf("%d",(a+i));
 
 /* Get the elements of the array b */
 for(i=0;i<n;i++)
  scanf("%d",(b+i));
 /* Counter variable for array a */
 l=0; 
 
 /* Counter variable for array b */
 r=0;
 
 /* Counter variable for array temp */
 j=0;
 
 /* Until either one of the array becomes empty, store the elements in ascending order in temp */
 while(l<n && r<n)
 {
  if(*(a+l)<*(b+r))
  temp[j++]=a[l++];
  else
  temp[j++]=b[r++];
 }
 
 /* If still array b is not empty but array a is empty, copy all the remaining elements of the array b
 to temp */
 if(l==n)
 {
  while(r<n)
  temp[j++]=b[r++];
 }
 
 /* Else if still array a is not empty but array b is empty, copy all the remaining elements of the array a
 to temp */
 else
 {
  while(l<n)
  temp[j++]=a[l++];
 }
 
 /* finally print the temp array to get 2*n merged elements from the two sorted arrays */
 for(i=0;i<2*n;i++)
  printf("%d ",*(temp+i));
  
 printf("\n");
 
        /* Reallocate memory of a to store elements of size 2*n */
 a=(int*)realloc(a,2*n);
        
       /* copy the elements of array temp to array a */
 for(i=0;i<2*n;i++)
      *(a+i)=*(temp+i);

 printf("\n");

        /* Print the array a, which is merged now */
 for(i=0;i<2*n;i++)
 printf("%d ",*(a+i));

 return 0;
}