Cup Swapping

There are three cups on a table, at positions A, B, and C. At the start, there is a ball hidden under the cup at position B.

However, I perform several swaps on the cups, which is notated as two letters. For example, if I swap the cups at positions A and B, I could notate this as AB or BA.

Create a function that returns the letter position that the ball is at, once I finish swapping the cups. The swaps will be given to you as a list.

Worked Example

cup_swapping(["AB", "CA", "AB"]) ➞ "C"

# Ball begins at position B.
# Cups A and B swap, so the ball is at position A.
# Cups C and A swap, so the ball is at position C.
# Cups A and B swap, but the ball is at position C, so it doesn't move.

Examples

cup_swapping(["AB", "CA"]) ➞ "C"

cup_swapping(["AC", "CA", "CA", "AC"]) ➞ "B"

cup_swapping(["BA", "AC", "CA", "BC"]) ➞ "A"

Notes

• A swap could be notated in two different ways, since both ways end up with the same outcome.
• All swaps will be notated as capital letters and will be valid.
• You cannot swap a cup with itself.