binary search recursive ( ds lab 1) 3rd sem

#include<stdio.h>
int binary(int l,int r,int ar[],int n)
{
    int m=(l+r)/2;
    if(l>r)
        return -1;
        else if(ar[m]==n)
            return m;
        else if(n>ar[m])
            binary(m+1,r,ar,n);
        else if(n<ar[m])
            binary(l,m-1,ar,n);
}
int main()
{
    int a,arr[100],i,n;
   for(i=0;;i++)
   {
       scanf("%d",&a);
       if(a>=0)
        arr[i]=a;
       else
        break;
   }
   scanf("%d",&n);
   int l,r;
   l=0,r=i-1;
   int res=binary(l,r,arr,n);
   printf("%d",res);
}