freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-355-maximal-coprime-subset.md

---
id: 5900f4d01000cf542c50ffe2
title: 'Problem 355: Maximal coprime subset'
challengeType: 5
forumTopicId: 302015
dashedName: problem-355-maximal-coprime-subset
---

# --description--

Define $Co(n)$ to be the maximal possible sum of a set of mutually co-prime elements from $\\{1, 2, \ldots, n\\}$. For example $Co(10)$ is 30 and hits that maximum on the subset $\\{1, 5, 7, 8, 9\\}$.

You are given that $Co(30) = 193$ and $Co(100) = 1356$.

Find $Co(200\\,000)$.

# --hints--

`maximalCoprimeSubset()` should return `1726545007`.

```js
assert.strictEqual(maximalCoprimeSubset(), 1726545007);
```

# --seed--

## --seed-contents--

```js
function maximalCoprimeSubset() {

  return true;
}

maximalCoprimeSubset();
```

# --solutions--

```js
// solution required
```