Concatenation of Linked List Alternatively

Hi, This program is about implementation of Concatenation of linked list alternatively. 

If you have any doubt regarding this program or any concept of C then please send me at khimanichirag@gmail.com or post a comment.

suggestion always appreciable

         #include<stdio.h>   
         #include<conio.h>   
         void concate_alternative();   
         typedef struct node   
         {   
           int data;   
           struct node *link;   
         }node;  
         node *first1=NULL,*last1,*first2=NULL,*last2;   
         void main()   
         {   
           int i=0;   
           node *temp;   
           printf("Enter the data in first link list");   
           do   
           {   
                  clrscr();   
                   temp=(node*)malloc(sizeof(node));   
                  i++;   
                  if(first1==NULL)   
                  {   
                     first1=temp;   
                     last1=temp;   
                     last1->link=NULL;   
                  }   
                  else   
                  {   
                     last1->link=temp;   
                     last1=temp;   
                     last1->link=NULL;   
                  }   
                   printf("\nEnter the %d element for first linked list: ",i);   
                   scanf("%d",&(last1->data));   
                   printf("\nYou want to enter more data(Y/N)");   
           }while(getch()=='y');  
           printf("\n\n\nYour first link list is:");   
           temp=first1;   
           while(temp!=NULL)   
           {   
                   printf("%d ",temp->data);   
              temp=temp->link;   
           }   
           getch();   
      //===========Scan data for second linked list=============   
           i=0;   
           clrscr();   
           printf("\n\nEnter the data in second link list");   
           do   
           {   
                   clrscr();   
                   temp=(node*)malloc(sizeof(node));   
                  i++;   
                   if(first2==NULL)   
                   {   
                    first2=temp;   
                    last2=temp;   
                    last2->link=NULL;   
                   }   
                   else   
                   {   
                    last2->link=temp;   
                    last2=temp;   
                    last2->link=NULL;   
                   }   
                  printf("\nEnter the %d element for second linked list: ",i);   
                  scanf("%d",&(last2->data));   
                  printf("\nYou want to enter more data(Y/N)");   
            }while(getch()=='y');   
            printf("\n\n\nYour second link list is:");   
            temp=first2;   
            while(temp!=NULL)   
            {   
                  printf("%d ",temp->data);   
                  temp=temp->link;   
            }   
            concate_alternative();   
            getch();   
      }   
         void concate_alternative()   
         {   
           node *temp1,*temp2,*first3=NULL,*last3,*temp;   
            int i=0;   
            temp1=first1;   
            temp2=first2;   
            while(temp1!=NULL && temp2!=NULL)   
            {   
                   if(i%2==0)   
                   {   
                      if(first3==NULL)   
                      {   
                           first3=temp1;   
                           last3=temp1;   
                      }   
                      else   
                      {   
                           last3->link=temp1;   
                           last3=temp1;   
                      }   
                      temp1=temp1->link;   
                      i++;   
                   }   
                   else   
                   {   
                      if(first3==NULL)   
                      {   
                           first3=temp2;   
                           last3=temp2;   
                      }   
                      else   
                      {   
                         last3->link=temp2;   
                         last3=temp2;   
                      }   
                      temp2=temp2->link;   
                    i++;   
                   }   
       }   
       if(temp1==NULL)   
       {   
             last3->link=temp2;   
       }   
       else if(temp2==NULL)   
       {   
             last3->link=temp1;   
       }   
       else   
       {   
             printf("\n\nCode is not working properly");   
       }   
       printf("\n\nYour final list is:");   
       temp=first3;   
       while(temp!=NULL)   
       {   
             printf("%d ",temp->data);   
         temp=temp->link;   
       }    
    }