Add solutions for part 1

projects/04/mult/Mult.asm

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/04/Mult.asm
+
+// Multiplies R0 and R1 and stores the result in R2.
+// (R0, R1, R2 refer to RAM[0], RAM[1], and RAM[2], respectively.)
+
+  // R2 = 0
+  @R2
+  M = 0
+  // i = 0
+  @i
+  M = 0
+
+(LOOP)
+  // (if i >= R0 <=> if i - R0 >= 0) goto END
+  @i
+  D = M
+  @R0
+  D = D - M
+  @END
+  D;JGE
+
+  // R2 = R2 + R1
+  @R1
+  D = M
+  @R2
+  M = M + D
+
+  // i++
+  @i
+  M = M + 1
+
+  // goto LOOP
+  @LOOP
+  0;JMP
+
+(END)
+  @END
+  0;JMP