Set: pp::colors
  Set: pp::unicode
  Assumed: a
  Assumed: b
  Assumed: c
  Assumed: d
  Assumed: e
  Assumed: f
f + (c + f + d) + (e * (a + c) + (d + a))
i: 1 ====>
d + (f + (c + f) + (a + d + (e * a + e * c)))
i: 2 ====>
a + (d + (c + (f + f) + (d + (e * a + e * c))))
i: 3 ====>
a + (d + (d + (c + (f + f) + (e * a + e * c))))
i: 4 ====>
a + (c + (d + (d + (f + f + (e * a + e * c)))))
i: 5 ====>
a + (c + (d + (d + (f + (f + (e * a + e * c))))))
i: 6 ====>
a + (c + (d + (d + (f + (f + (e * a + e * c))))))