FIBONACCI   PUSH   R1
            PUSH   R2
            PUSH   R3

            MOVE   0,  R1
            MOVE   1,  R2

FIB_LOOP    SUB    R0,  1, R0
            JP_Z   FIB_DONE

            MOVE   R2, R3
            ADD    R1, R2, R2
            MOVE   R3, R1

            JP     FIB_LOOP

FIB_DONE    MOVE   R2, R0

            POP    R3
            POP    R2
            POP    R1

            RET