Interleaving explorer: watch updates get lost

Two threads A and B each increment a shared counter (initially 0) k times. Each increment is three steps: load (r = counter), add (r = r + 1), store (counter = r). Each thread has its own register r.

Input: first line k, second line a schedule: a string of A and B characters saying which thread executes its next step (it must contain exactly 3k A's and 3k B's; otherwise print Invalid schedule and stop).

1. Execute the schedule and print one line per step: A load (rA=0), B add (rB=1), A store (counter=1).
2. Print Final counter: X (expected 2k) and Lost updates: 2k - X.
3. Enumerate all interleavings of the 6k steps (every schedule with 3k A's and 3k B's), and print All interleavings: N and Final values: v=count ... for every possible final value in increasing order.

Input:

1
ABABAB

Output:

A load (rA=0)
B load (rB=0)
A add (rA=1)
B add (rB=1)
A store (counter=1)
B store (counter=1)
Final counter: 1 (expected 2)
Lost updates: 1
All interleavings: 20
Final values: 1=18 2=2