There are many ways to represent arithmetic expressions.

We commonly use infix notation where operations are put in between values (i.e. ), but another less well-known method is prefix notation. This is where operations are put before values. For example, if we want to add two numbers we would write `+ x y`

instead of `x + y`

. Furthermore, brackets are used to enforce order of evaluation.

The formal definition of prefix notation we will be using is as any one of the following options:

`x`

, where`x`

is an integer.`(+ x y)`

, where`x`

and`y`

are valid prefix notation expressions. The result of this expression is .

Your objective today is to evaluate prefix notation expressions **that only involve addition**.

#### Input Specification

The first and only line of input contains a valid prefix notation expression. You can expect the expression to only consist of the following characters: `0123456789()+-`

(and the space: ` `

)

#### Output Specification

The value of that expression.

#### Constraints

Any integer in the given expression will satisfy the following inequality: .

, where denotes the length of the prefix notation expression.

#### Sample Input

`(+ 1 (+ (+ (+ 3 4) -2) 5))`

#### Sample Output

`11`

#### Sample Explanation

Here is the sample input being simplified:

`(+ 1 (+ (+ (+ 3 4) -2) 5))`

`(+ 1 (+ (+ 7 -2) 5))`

`(+ 1 (+ 5 5))`

`(+ 1 10)`

`(11)`

`11`

## Comments

I like how the input specification says that the input will only consist of “ 0123456789()+”, yet the sample input has a “-“.

fixed

I like how the title says its a recursion problem but literally none of the answers use recursion

I kept getting a WA on the second test case because the input was simply just an integer. Don't forget to add a test case for this.

If you got this problem in brain

**, I have respect for you.My solution is showing "MemoryError" for almost all of the methods I try. For some other methods, it may show different errors, but the consistent pattern is that the first two inputs show AC and the next one fails for some reason. I am using Python 3.

Edit: Nevermind, it was probably the eval() I was using...