You actually don't need to import the `range_check_ptr` but actually the `range_check` built-in (check this [link](https://www.cairo-lang.org/docs/how_cairo_works/builtins.html#the-builtins-directive)). Change your code to 
```
%builtins range_check
from starkware.cairo.common.math import abs_value

func main{range_check_ptr}() {
    let x = abs_value(-1);
    return ();
}
```

and it should compile and run.

# Hello world!

I try to implement the function `abs_value` of the package `starkware.cairo.common.math` but i have this error

```
AssertionError: Expected main to contain the following arguments (in this order): ['range_check_ptr_ptr']. Found: ['range_check_ptr'].
```

I dont understand the error. 

Can someone explain the error to me, why it happens ? 

> I am doing the challenge #17daysOfCairo of the day 3


Full code

```
%builtins range_check_ptr
from starkware.cairo.common.math import abs_value

func main{range_check_ptr}() {
    let x = abs_value(-1);
    return ();
}
```


chocolaite

AssertionError with range_check_ptr_ptr

How do I run a Pathfinder node?

I use `ec.getKeyPair("copy paste from argent x")` to initialize the account however i get the response is invalid, with respect to the public key

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Invalid response while using `ec.getKeyPair("copy

Does AA support bundling multiple operations at once?
---

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Does Account Abstraction (StarkNet) support bundling multiple operations at once?

What will the bundler ecosystem look like in AA?

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What will the bundler ecosystem look like in Account Abstraction?

### *From Newton AI*
*"Assembly" is a low-level language that is used to write smart contracts for the Ethereum Virtual Machine (EVM). It is similar to machine code, which is the code that is run directly on a computer's central processing unit (CPU). Assembly is often used in Solidity contracts to perform complex tasks or to optimize the performance of the contract.*

*If a Solidity contract contains assembly code, it is important to be careful when working with it, as it can be difficult to read and understand. Additionally, certain assembly instructions, known as "special EVM calls," can have unintended consequences if not used correctly. For example, some special EVM calls can cause a contract to consume an excessive amount of gas, which can make it more expensive for users to interact with the contract.*

*It is generally recommended to avoid using assembly in Solidity contracts if possible, as it can make the contract more difficult to understand and maintain. If you do need to use assembly, it is important to thoroughly test and debug the contract to ensure that it functions as intended.*

What if my solidity contract contains Assembly or special EVM calls ?

Are there rewards for running a Pathfinder node?

Hello! This is day 14 of the 17 days of the Cairo Challenge. And I have no idea how to solve the [playground](https://www.cairo-lang.org/playground/) exercise “Hints”.  Perhaps you can help me?

```
// The following function uses hints to efficiently compute the square root `res`
// of the argument `n`.
// The idea is that the verifier only needs to be convinced that res * res = n,
// it doesn't really care how res was computed.
// In such cases, we don't have to compute res in pure Cairo - we can write a
// piece of Python code inside the Cairo program, which is called a "hint".
// A hint is a piece of code that the prover runs to initialize
// some memory cells. Note that it is completely transparent from the verifier's
// point of view, so the result of the hint *must* be verified using pure Cairo
// instructions (e.g., the "assert n = res * res" instruction below).
//
// 1. Comment out the line "assert n = res * res;" and run the code. Does it still output
//    the expected value? Can you explain why the assert is nonetheless essential?
//    Hint: Recall that from the verifier's point of view, the hint does not exist.
// 2. Uncomment the assert line and change the function to compute the fourth
//    root.

%builtins output

from starkware.cairo.common.serialize import serialize_word

// Computes the square root (over the integers) of `n`.
// Prover assumption: The square root exists.
func sqrt(n) -> (res: felt) {
    alloc_locals;
    local res;

    // Set the value of res using a Python hint.
    %{
        import math

        # Use the ids variable to access the value of a Cairo variable.
        ids.res = int(math.sqrt(ids.n))
    %}

    // From the verifier's point of view, the hint is completely transparent.
    // The following line guarantees that `res` is the square root
    // (either the positive or negative) of `n`.
    assert n = res * res;
    return (res=res);
}

func main{output_ptr: felt*}() {
    let (res) = sqrt(256);
    serialize_word(res);
    return ();
}
```

---

> Answers to this question are a part of the ✨ 17 days of Cairo Lang with Playground & Newton. ✨
> 

*Vote for your favorite answer - the best answer will win a $10 award. A new day – a new reward! During the next 17 days, our goal is to attract more developers to the Cairo language and to systematize the knowledge of Cairo lang. [Read rules](https://www.notion.so/17-days-of-Cairo-Lang-with-Newton-550dfcda6a2d449ca468be293c776578)*

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AssertionError with range_check_ptr_ptr

Hello world!

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