def binary_search(arr, target):
                    left = 0
                    right = len(arr) - 1
                    while left <= right:
                        mid = (left + right) // 2
                        if arr[mid] == target:
                            return mid
                        elif arr[mid] < target:
                            left = mid + 1
                        else:
                            right = mid - 1
                    return -1