"Puzzle - you have A, A', B, B', C, C'. A, A' etc. differ in weight by 1 ounce. Separate the heavy and light using a balance only twice."
a = 1
A = 2
b = 1
B = 2
c = 1
C = 2
# First weight
(a + b + c) < (A + B + C)
True
# Second weight
a < A
True
Then lower case letters are lighter.