User blog comment:Edwin Shade/The Challenge Of Minimum Rings/@comment-1605058-20171102114301/@comment-30754445-20171102152956

The 1/2 and the f1 in the last term cancel out, so:

4+f3(3)/2+f2(f2(3))

Also, f2(f2(3)) = f2(24) = 402653184

So we can write this answer as:

f3(3)/2+402653184

(or alternatively: 3×2402653210+402653184)