import java.util.*;import java.io.*;// Code Structure of this Virtual Machineclass Instr {    int fct;    int level;    int adr;    Instr(int f, int l, int a) {        fct = f;        level = l;        adr = a;    }}public class CodeSegment {    // Instruction types    public static final int lit = 0;    public static final int opr = 1;    public static final int lod = 2;    public static final int sto = 3;    public static final int cal = 4;    public static final int inct = 5;    public static final int jmp = 6;    public static final int jpc = 7;    // opcodes for opr    public static final int opReturn = 0;    public static final int opUnaryMinus = 1;    public static final int opPlus = 2;    public static final int opMinus = 3;    public static final int opTimes = 4;    public static final int opDiv = 5;    public static final int opOdd = 6;    public static final int opEqual = 8;    public static final int opNotEqual = 9;    public static final int opLess = 10;    public static final int opGreaterEqual = 11;    public static final int opGreater = 12;    public static final int opLessEqual = 13;    public static final int opWrite = 14;    public static final int opNewLine = 15;    public static final int opRead = 16;            // Size of a standard stack frame    public static final int frameSize = 3;    ArrayList code;    String mnemonic[];    CodeSegment() {	    code = new ArrayList();	    mnemonic = new String[jpc + 1];	    mnemonic[lit] = "lit";	    mnemonic[opr] = "opr";	    mnemonic[lod] = "lod";	    mnemonic[sto] = "sto";	    mnemonic[cal] = "cal";	    mnemonic[inct] = "int";	    mnemonic[jmp] = "jmp";	    mnemonic[jpc] = "jpc";    }    public void gen (int fct, int level, int addr) {	    code.add(new Instr(fct, level, addr));    }        public void setAddrField(int instradr, int adrVal) {	    try {	        Instr i = (Instr) code.get(instradr);	        i.adr = adrVal;	    } catch (IndexOutOfBoundsException e) {	    }    }    public int nextInstrAdr() {	    return code.size();  // Current code position    }    public void list(PrintWriter out, int firstadr, int lastadr) {        try {    	    for (int i=firstadr; i <= lastadr; i++) {    		    Instr inst = (Instr) code.get(i);    		    out.println(StringJustify.right(String.valueOf(i), 11) +     			    "  " + StringJustify.left(mnemonic[inst.fct], 5) +     			    StringJustify.right(String.valueOf(inst.level), 3)+    			    StringJustify.right(String.valueOf(inst.adr), 5));    	    }    	} catch (IndexOutOfBoundsException e) {    	}    }    public void interpret(PrintWriter out) throws IOException {	    final int stacksize = 500;	    int s[] = new int[stacksize];    	int pc;    // p in pl0.p    	int fp;    // b in pl0.p    	int sp;    // t in pl0.p    	Instr i;        	out.println(" START PL/0");    	sp = -1;    	fp = 0;    	pc = 0;    	s[0] = s[1] = s[2] = 0;    	do {    	    i = (Instr) code.get(pc);    	    pc++;    	    switch (i.fct) {    	                	    case lit:            		sp++;            		s[sp] = i.adr;        		break;            	    case opr:        		switch(i.adr) {            		case opReturn:    // return            		    sp = fp - 1;            		    pc = s[sp + 3];            		    fp = s[sp + 2];            		    break;                        		case opUnaryMinus:            		    s[sp] = -s[sp];            		    break;                        		case opPlus:            		    sp--;            		    s[sp] += s[sp+1];            		    break;                        		case opMinus:            		    sp--;            		    s[sp] -= s[sp+1];            		    break;                        		case opTimes:            		    sp--;            		    s[sp] *= s[sp+1];            		    break;                        		case opDiv:            		    sp--;            		    s[sp] = s[sp] / s[sp+1];            		    break;                        		case opOdd:            		    s[sp] = s[sp] % 2 == 0 ? 0 : 1;            		    break;                        		case opEqual:            		    sp--;            		    s[sp] = bool2int(s[sp] == s[sp+1]);            		    break;            		                		case opNotEqual:            		    sp--;            		    s[sp] = bool2int(s[sp] != s[sp+1]);            		    break;            		                		case opLess:            		    sp--;            		    s[sp] = bool2int(s[sp] < s[sp+1]);            		    break;            		                		case opGreaterEqual:            		    sp--;            		    s[sp] = bool2int(s[sp] >= s[sp+1]);            		    break;            		                		case opGreater:            		    sp--;            		    s[sp] = bool2int(s[sp] > s[sp+1]);            		    break;            		                		case opLessEqual:            		    sp--;            		    s[sp] = bool2int(s[sp] <= s[sp+1]);            		    break;                                            case opWrite:                        out.println(StringJustify.right(String.valueOf(s[sp]), 11));                        sp--;                        break;                                            case opNewLine:                        out.println("\n");                        break;                                            case opRead:                        System.out.print(">");                        BufferedReader in                               = new BufferedReader(new InputStreamReader(System.in));                        String src_num = in.readLine();                        s[sp+1] = Integer.valueOf(src_num).intValue();                        sp++;                        break;            		    }        		    break;            	    case lod:            		sp++;            		s[sp] = s[base(s, fp, i.level) + i.adr];        		    break;                	    case sto:            		s[base(s, fp, i.level) + i.adr] = s[sp];            		//out.println(StringJustify.right(String.valueOf(s[sp]), 11));            		sp--;        		    break;                	    case cal:  // generate new block mark            		s[sp+1] = base(s, fp, i.level);            		s[sp+2] = fp;            		s[sp+3] = pc;            		fp = sp + 1;            		pc = i.adr;        		    break;                	    case inct:            		sp = sp + i.adr;        		    break;                	    case jmp:            		pc = i.adr;        		    break;                	    case jpc:            		if (s[sp] == 0) {            		    pc = i.adr;            		}            		sp--;           		    break;           		    	    }    	} while (pc != 0);    	out.println(" END PL/0");    }    int base(int s[], int fp, int level) {	    while (level > 0) {	        fp = s[fp];	        level--;	    }	    return fp;    }    int bool2int(boolean b) {        return b ? 1 : 0;    }}