CONCATENATION OF A SINGLY LINKED LIST IN C

#include<stdio.h>
#include<stdlib.h>
struct NODE
{
 int x;
 struct NODE *pnext;
};
struct LIST
{
 int count;
 struct NODE *pfirst;
};
struct LIST *PL1,*PL2;
void createlist(struct LIST *);
void insertnode(struct LIST *,struct NODE *);
void listconcat(struct LIST *,struct LIST *);
struct NODE * createnode(void);
void display(struct LIST *);

int main()
{
 PL1=(struct LIST *)malloc(sizeof(struct LIST));
 PL2=(struct LIST *)malloc(sizeof(struct LIST));
 if((!PL1)||(!PL2))
 {
 printf("NO <Memory \n");
 return 0;
 }
 else
 {
 PL1->count=0;
 PL2->count=0;
 PL1->pfirst=NULL;
 PL2->pfirst=NULL;

 createlist(PL1);
 createlist(PL2);

 display(PL1);
 display(PL2);

 listconcat(PL1,PL2);

 display(PL1);
 display(PL2);
 return 0;
 }
}
struct NODE * createnode(void)
{
 int n=0;
 printf("enter a number :\n");
 scanf("%d",&n);
 struct NODE * pt=(struct NODE *)malloc(sizeof(struct NODE));
 if(!pt)
 return NULL;
 else
 {
  pt->x=n;
  return pt;
 }
}
void display(struct LIST *l)
{
 struct NODE *pt=l->pfirst;
 if(!pt)
 {
 printf("Empty list\n");
 }
 else
 {
  printf("The List has  :\n");
  do{
  printf("%d\t",pt->x);
  pt=pt->pnext;
   }while(pt);
 }
}
void createlist(struct LIST *pl)
{
 struct NODE * pnew=NULL;
 int n,i=0;
 printf("enter number of elements :\n");
 scanf("%d",&n);
 for(i=0;i<n;i++)
 {
  pnew=createnode();
  insertnode(pl,pnew);
 }
 return ;
}
void insertnode(struct LIST *pl,struct NODE *pnew)
{
 struct NODE *pt=NULL;
 if(pl->pfirst==NULL)
 pl->pfirst=pnew;
 else
 {
 pt=pl->pfirst;
  while(pt->pnext)
pt=pt->pnext;
  pt->pnext=pnew;
 }
 (pl->count)++;
 return ;
}
void listconcat(struct LIST *l1,struct LIST *l2)
{
 struct NODE *ptm=NULL,*pl=l1->pfirst,*pt=l2->pfirst;
 while(pl->pnext!=NULL)
pl=pl->pnext;
 while(pt)
 {
 ptm=(struct NODE *)malloc(sizeof(struct NODE));
 ptm->x=pt->x;
 ptm->pnext=NULL;
 pl->pnext=ptm;
 pl=pl->pnext;
 pt=pt->pnext;
 (l1->count)++;
 }
 return ;
}