MOV AX,1245H
MOV CL,4
ROL AX,CL
DEC AX
MOV CX,4
MUL CX
HLT
MOV AX,1245H ;AX=1245H
ROL AX,CL ;AX=5124H
DEC AX ;AX=5123H
MUL CX ;AX=448CH