Give me the correct code with c# please

Initial value of shared variable m is equal to 0 . Four threads A,B,Y,Z use this variable as follows: Processes A and B increase the value of m by 1 . Processes Y and Z decrease the value of m by 1 . Since m is shared, each process protects the critical region using semaphore S initialized to 2 . Run your program to show that it is possible that m 's value can be equal 2 after all processes run once