c program for fibonacci

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

main(){
       int a,lim,i,F1=1,F2=1,F3;
      
      
       printf("Enter the limiting step:\t");
       scanf("%d",&lim); 
       if(a==1)
       printf("%d",a);
       for(i=1;i<=lim;i++){
                           F3=F1+F2;
                           printf("%d ",F3);
                          
                           F1=F2;
                           F2=F3;
                           }