Circle sorted array searching.

Question:
Given a circle sorted array, please write a function to search a number and output its position.

Example:
Find number 6 in array { 1,2,3,4,5,6,7 }, output is 5
Find number 6 in array { 5,6,7,1,2,3,4 }, output is 1

My Answer:  (I am no sure if it is correct.)

#include "stdafx.h"
#include 

using namespace std;

int binarySearch(int n, int* a, int l, int r);

int _tmain(int argc, _TCHAR* argv[])
{
 int a[7] = { 4, 5, 6, 7, 1, 2, 3 };
 
 cout << binarySearch(6, a, 0, 6) << endl;
 cout << binarySearch(2, a, 0, 6) << endl;
 cout << binarySearch(5, a, 0, 6) << endl;

 cin.get();
 return 0;
}

int binarySearch(int n, int* a, int l, int r)
{
 int i = (l + r) / 2;
 if (n == a[i])
  return i;

 if (a[l] < a[r])
 {
  if (n > a[i])
  {
   l += 1;
  }
  else
  {
   r = i - 1;
  }
 }
 else
 {
  if (n > a[i] || n < a[l])
  {
   l += 1;
  }
  else
  {
   r = i - 1;
  }
 }

 return binarySearch(n, a, l, r);
}