2020牛客暑期多校训练营（第九场）A

题目描述

Groundhog took a math class. In this class, his math teacher said, any positive integer can be represented by the power of $2$ . For example, $137=2^7+2^3+2^0$ .
And powers are expressed in parentheses. That is, $a(b)$ stands for $a^b$ . Therefore, $137$ can be expressed as $137=2(7)+2(3)+2(0)$ .
Further more,for $7=2^2+2+2^0$ is expressed with $2$ , $3=2+2^0$ ,137 can be finally expressed as $137=2(2(2)+2+2(0))+2(2+2(0))+2(0)$ .
Another example, $1315=2^{10}+2^8+2^5+2+1 =$ $2(2(2+2(0))+2)+2(2(2+2(0)))+2(2(2)+2(0))+2+2(0)$ .
Groundhog feels amazing and wants you to write a program to simulate the above content. You need to read in an expression that is a power of $2$ and calculate its value.

输入描述

Given a string, indicating the power representation.

输出描述

Output the original number.

示例1

输入

2(2(2+2(0))+2)+2(2(2+2(0)))+2(2(2)+2(0))+2+2(0)

输出

备注

The range of answers is $[10,10^{180}]$ ，and the length of the input data shall not exceed $20000$ .

分析

题面的本质是定义了一个表达式，然后计算表达式的值；而众所周知， $\text{Python}$ 的 $\text{eval}$ 函数可以直接输出表达式的值。
题中定义 $a(b)$ 为 $a^b$ ，而 $\text{Python}$ 中认为 $a\ast\ast (b)$ 为 $a^b$ 。因此，只需要将表达式中的 $($ 替换为 $\ast\ast($ ，就能用 $\text{eval}$ 函数计算表达式的值。

代码

"""***************************************************
Copyright: 11D_Beyonder All Rights Reserved
Author: 11D_Beyonder
Problem ID: 2020牛客暑期多校训练营（第九场） Problem A
Date: 9/3/2020
Description: The Basis Of Python
***************************************************"""
print(eval(input().replace('(','**(')))