def assembly_rec(num):
    check_assembly = calculate_assembly(num)
    if check_assembly is False:
        return -1
    return check_assembly

def calculate_assembly(num,assembly = 2,cur_num = 1):
    if cur_num>num:
        return False
    if cur_num == num:
        return assembly-1
    return calculate_assembly(num,assembly+1,cur_num*assembly)