C program merging two sorted single linked lists

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

struct node
{
	int info;
	struct node *link;
};

struct node *create(struct node *start);
struct node *insert_s(struct node *start,int data);
struct node *insert(struct node *start,int data);
void display(struct node *start );
void merge(struct node *p1,struct node *p2);
main()
{
	struct node *start1=NULL,*start2=NULL;	
	start1=create(start1);
	start2=create(start2);
	
	printf("List1 : ");	
	display(start1);
	printf("List2 : "); 
	display(start2);
	merge(start1, start2);
}/*End of main()*/

void merge(struct node *p1,struct node *p2)
{
	struct node *start3;
	start3=NULL;
	
	while(p1!=NULL && p2!=NULL)
	{
		if(p1->info < p2->info)
		{
			start3=insert(start3,p1->info);
			p1=p1->link;
		}
		else if(p2->info < p1->info)
		{
			start3=insert(start3,p2->info);
			p2=p2->link;
		}
		else if(p1->info==p2->info)
		{
			start3=insert(start3,p1->info);
			p1=p1->link;
			p2=p2->link;
		}
	}
	/*If second list has finished and elements left in first list*/
	while(p1!=NULL)
	{
		start3=insert(start3,p1->info);
		p1=p1->link;
	}
	/*If first list has finished and elements left in second list*/
	while(p2!=NULL)
	{
		start3=insert(start3,p2->info);
		p2=p2->link;
	}
	printf("Merged list is : ");
	display(start3);
}

struct node *create(struct node *start )
{
	int i,n,data;
	printf("Enter the number of nodes : ");
	scanf("%d",&n);
	start=NULL;
	for(i=1;i<=n;i++)
	{
		printf("Enter the element to be inserted : ");
		scanf("%d",&data);
		start=insert_s(start, data);
	}
	return start;
}/*End of create_slist()*/

struct node *insert_s(struct node *start,int data)
{
	struct node *p,*tmp;
	tmp=(struct node *)malloc(sizeof(struct node));
	tmp->info=data;
	/*list empty or data to be added in beginning */
	if(start==NULL || data<start->info)
	{
		tmp->link=start;
		start=tmp;
		return start;
	}
	else
	{
		p=start;
		while(p->link!=NULL && p->link->info < data)
			p=p->link;
		tmp->link=p->link;
		p->link=tmp;
	}
	return start;
}/*End of insert_s()*/

struct node *insert(struct node *start,int data)
{
	struct node *p,*tmp;
	tmp=(struct node *)malloc(sizeof(struct node));
	tmp->info=data;
	/*If list is empty*/
	if(start==NULL)
	{
		tmp->link=start;
		start=tmp;
		return start;
	}
	else	/*Insert at the end of the list*/
	{
		p=start;
		while(p->link!=NULL)
			p=p->link;
		tmp->link=p->link;
		p->link=tmp;
	}
	return start;
}/*End of insert()*/

void display(struct node *start)
{
	struct node *p;
	if(start==NULL)
	{
		printf("List is empty\n");
		return;
	}
	p=start;
	while(p!=NULL)
	{
		printf("%d ",p->info);
		p=p->link;
	}
	printf("\n");
}