def binary_search(A, left, right, val):
    if left <= right:
        pivot = (left + right) // 2
        if A[pivot] == val:
            return True
        elif A[pivot] > val:
            return binary_search(A, left, pivot-1, val)
        else:
            return binary_search(A, pivot+1, right, val)
    else:
        return False

A = [1, 2, 3, 4, 5, 6, 7]
N = len(A)
binary_search(A, 0, N - 1, 5)
