data/problems/71.yml
---
:id: 71
:name: Ordered fractions
:url: https://projecteuler.net/problem=71
:content: |+
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 2/5 is the fraction immediately to the left of 3/7.
By listing the set of reduced proper fractions for _d_ ≤ 1,000,000 in ascending order of size, find the numerator of the fraction immediately to the left of 3/7.