def bsearch(arr, x):    
    def recurse(min, max):        
        if min > max:   
            return None 
            
        mid = (min + max) // 2
        
        if x == arr[mid]:
            return mid 
            
        if x > arr[mid]:
            min = mid + 1
        else:
            max = mid - 1
            
        return recurse(min, max)
            
    return recurse(0, len(arr) - 1)
    
arr = [1,2,3,4,5]
for i in range(7):
    print(bsearch(arr, i))