freeCodeCamp/curriculum/challenges/chinese/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, ..., 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(200000).

# --hints--

`euler355()` should return 1726545007.

```js
assert.strictEqual(euler355(), 1726545007);
```

# --seed--

## --seed-contents--

```js
function euler355() {

  return true;
}

euler355();
```

# --solutions--

```js
// solution required
```