id	title	challengeType	forumTopicId	dashedName
5900f3b41000cf542c50fec7	Problem 72: Counting fractions	5	302185	problem-72-counting-fractions

--description--

Consider the fraction, n/d, where n and d are positive integers. If n<d and HCF(n,d)=1, it is called a reduced proper fraction.

If we list the set of reduced proper fractions for d ≤ 8 in ascending order of size, we get:

1/8, 1/7, 1/6, 1/5, 1/4, 2/7, 1/3, 3/8, 2/5, 3/7, 1/2, 4/7, 3/5, 5/8, 2/3, 5/7, 3/4, 4/5, 5/6, 6/7, 7/8

It can be seen that there are 21 elements in this set.

How many elements would be contained in the set of reduced proper fractions for d ≤ 1,000,000?

--hints--

countingFractions() should return a number.

assert(typeof countingFractions() === 'number');

countingFractions() should return 303963552391.

assert.strictEqual(countingFractions(), 303963552391);

function countingFractions() {

  return true;
}

countingFractions();

// solution required