I am putting the input number n into the variable $M0 ...: $M0 = 16
...simulating the machine language program at the bottom of this page...
before: $M2 = 0 $M0 = 16
after: $M2 = 16 $M0 = 16
0: $M0 = 16 $M1 = 4 $M2 = 16
1: $M0 = 16 $M1 = 4 $M2 = 4
2: $M0 = 16 $M1 = 4 $M2 = 16
3: $M0 = 0 $M1 = 4 $M2 = 16
flow 2: $M0 = 0 $M1 = 4 $M2 = 16
the result: $M1 = 1