a == add 12 "twelve" empty
b == add 3 "three" a
c == add 8 "eight" b
d == add 15 "fifteen" c
e == add 1 "one" d
f == add 9 "nine" e
g == add 6 "six" f
h == add 10 "ten" g
i == add 11 "eleven" h
j == add 7 "seven" i
k == add 4 "four" j
l == add 13 "thirteen" k
m == add 0 "zero" l
n == add 14 "fourteen" m
o == add 2 "two" n
p == add 5 "five" o