Ordered fractions

Consider the fraction, \( \frac{n}{d} \), 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:

\[ \frac{1}{8},\frac{1}{7},\frac{1}{6},\frac{1}{5},\frac{1}{4},\frac{2}{7},\frac{1}{3},\frac{3}{8},\mathbf{\frac{2}{5}},\frac{3}{7},\frac{1}{2},\frac{4}{7},\frac{3}{5},\frac{5}{8},\frac{2}{3},\frac{5}{7},\frac{3}{4},\frac{4}{5},\frac{5}{6},\frac{6}{7},\frac{7}{8} \]

It can be seen that \( \frac{2}{5} \) is the fraction immediately to the left of \( \frac{3}{7} \).

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 \( \frac{3}{7} \).