C PROGRAM TO test the given number is an element of FIBONACCI sequence or not

#include<stdio.h>
#include<conio.h>

main()
{
      int n,pn,nn,cn,num,flag;

      clrscr();

      printf("\n\n Enter a number to test : ");
      scanf("%d",&num);

      pn = 0;
      nn = 1;
      cn = pn + nn;

      printf("\n\n FIBONACCI SERIES\n\n");
      printf(" %d %d",pn,nn);

      flag = 1;

      while(cn <= num)
      {
               printf(" %d",cn);
               if(num == cn)
                   flag = 0;
               pn = nn;
               nn = cn;
               cn = pn + nn;
      }

      if( flag == 0)
          printf("\n\n The given number %d is a fibonacci element\n\n",num);
      else
          printf("\n\n The given number %d is not a fibonacci element\n\n",num);

      return 0;
}