# Sum of Integers

Elementary
DE English FR PL UK ZH-HANS

Calculate sum of integers from 1 to given `N` (including).

Input: Integer (int).

Output: Integer (int).

Examples:

```assert sum_upto_n(1) == 1
assert sum_upto_n(2) == 3
assert sum_upto_n(3) == 6
assert sum_upto_n(4) == 10
```

How it’s used: this function can be used in a variety of mathematical and algorithmic contexts, such as in calculating the nth triangular number, determining the cost for certain operations in algorithms, etc.

Precondition:

• 1 ≤ N ≤ 900.

Settings
Code:
Other:
Invalid hot key. Each hot key should be unique and valid
Hot keys:
•  to Run Code: to Check Solution: to Stop:
CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

`pip3 install checkio_client`

`checkio --domain=py config --key=`

Sync solutions into your local folder

`checkio sync`

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

`checkio serv -d`

Alternatevly, you can install Chrome extension or FF addon

`checkio install-plugin`
`checkio install-plugin --ff`
`checkio install-plugin --chromium`

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

Pair Programming (Beta-version)

Welcome to Pair Programming! Engage in real-time collaboration on coding projects by starting a session and sharing the provided unique URL with friends or colleagues. This feature is perfect for joint project development, debugging, or learning new skills together. Simply click 'Start Session' to begin your collaborative coding journey!

Waiting for Pair Programming to start...

You are trying to join a pair programming session that has not started yet.

Please wait for the session creator to join.

Waiting for Pair Programming to reconnect...

It looks like the creator of the pair programming session closed the editor window.

It might happen accidentally, so that you can wait for reconnection.