freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-372-pencils-of-rays.english.md

---
id: 5900f4e11000cf542c50fff3
challengeType: 5
title: 'Problem 372: Pencils of rays'
---

## Description
<section id='description'>
Let R(M, N) be the number of lattice points (x, y) which satisfy M<x≤N, M<y≤N and  is odd.
We can verify that R(0, 100) = 3019 and R(100, 10000) = 29750422.
Find R(2·106, 109).



Note:  represents the floor function.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler372()</code> should return 301450082318807040.
    testString: assert.strictEqual(euler372(), 301450082318807040, '<code>euler372()</code> should return 301450082318807040.');

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function euler372() {
  // Good luck!
  return true;
}

euler372();
```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>