My solution to "mult problem" of nand2tetris course

// Multiplies R0 and R1 and stores the result in R2.
// (R0, R1, R2 refer to RAM[0], RAM[1], and RAM[2], respectively.)

// Put your code here.

    @2      // load result
    M=0     // zeroing result
    @3      // R[3] is the counter
    M=1     // set the counter to 1
(LOOP)
    @3      // load counter
    D=M     // store the counter in the data reg
    @1      // load 2nd factor
    D=D-M   // data = data - counter
    @END    // load end location
    D;JGT   // if data - counter > 0 goto END
    @0      // load 1st factor
    D=M     // store 1st factor in data reg
    @2      // load result
    M=M+D   // store result
    @3
    M=M+1   // increase the counter
    @LOOP
    0;JMP   // unconditionate jump to LOOP
(END)
    @END
    0;JMP   // infinte loop