===== ISTEM =====
Solve the following programming task.

TASK: TIK Register Machine

Write a function 'runTik(program)' that runs a program written in TIK, a small made-up language, and returns an array of the numbers it outputs.

Program text:
- Instructions are separated by newlines. Leading and trailing spaces on a line are ignored.
- Lines that are empty (or only spaces) and lines whose first non-space character is '#' are ignored and are not instructions.
- Within an instruction, tokens are separated by one or more spaces.

Machine:
- There are four registers named a, b, c and d. All start at 0.
- Every value stored in a register is reduced to the range 0..999 by taking it modulo 1000, always giving a non-negative result (for example -1 becomes 999 and 1003 becomes 3).
- An integer literal is an optional '-' followed by one or more digits ('+5' and '5.0' are not valid).
- An operand written as X below is either a register name or an integer literal. Its value is the register's value, or the literal reduced to 0..999 in the same way.

Instructions (R must be a register name, N must be an integer literal):
- set R X: R becomes the value of X.
- add R X: R becomes R plus the value of X.
- mul R X: R becomes R times the value of X.
- out X: appends the value of X to the output.
- jmp X N: if the value of X is not 0, the next instruction is the one N instructions away from this one (N may be negative; ignored lines are not counted). Otherwise execution continues with the next instruction.
Instruction names and register names are lowercase; anything else is invalid.

Running:
- Before running anything, check the whole program. If any line that is not ignored is not a valid instruction (unknown name, wrong number of operands, or an invalid register, literal or operand), throw an Error whose message is 'bad instruction at line K', where K is the 1-based line number of the first such line in the original text, counting ignored lines too. In that case nothing is run.
- Execution starts at the first instruction and stops normally when the next instruction position is before the first instruction or after the last one.
- A program may execute at most 10,000 instructions. If it has not stopped after executing 10,000 instructions, throw an Error with the message 'step limit'.

STARTER CODE (javascript):
function runTik(program) {
  // Write your code here
}

module.exports = { runTik };


RULES:
- Keep the function name and signature EXACTLY as given.
- Return working code only. No explanations.
- Put the code in a single ``` block.
- Try to solve it first. If you genuinely cannot, write only this single
  line instead of producing faulty code: CANNOT_SOLVE

===== HAM YANIT =====
```javascript
function runTik(program) {
  const registers = { a: 0, b: 0, c: 0, d: 0 };
  const instructions = [];

  const isRegister = (s) => /^[abcd]$/.test(s);
  const isInteger = (s) => /^-?\d+$/.test(s);

  function literalMod(s) {
    const negative = s[0] === "-";
    const digits = negative ? s.slice(1) : s;
    let value = 0;

    for (let i = 0; i < digits.length; i++) {
      value = (value * 10 + (digits.charCodeAt(i) - 48)) % 1000;
    }

    if (negative && value !== 0) value = 1000 - value;
    return value;
  }

  function parseOperand(s) {
    if (isRegister(s)) return { type: "reg", value: s };
    if (isInteger(s)) return { type: "lit", value: literalMod(s) };
    return null;
  }

  function operandValue(op) {
    return op.type === "reg" ? registers[op.value] : op.value;
  }

  function bad(lineNumber) {
    throw new Error("bad instruction at line " + lineNumber);
  }

  const lines = program.split("\n");

  for (let i = 0; i < lines.length; i++) {
    let line = lines[i];
    if (line.endsWith("\r")) line = line.slice(0, -1);

    const trimmed = line.trim();
    if (trimmed === "" || trimmed[0] === "#") continue;

    const tokens = trimmed.split(/ +/);
    const name = tokens[0];

    if (name === "set" || name === "add" || name === "mul") {
      if (tokens.length !== 3) bad(i + 1);
      if (!isRegister(tokens[1])) bad(i + 1);

      const operand = parseOperand(tokens[2]);
      if (!operand) bad(i + 1);

      instructions.push({
        op: name,
        reg: tokens[1],
        x: operand
      });
    } else if (name === "out") {
      if (tokens.length !== 2) bad(i + 1);

      const operand = parseOperand(tokens[1]);
      if (!operand) bad(i + 1);

      instructions.push({
        op: name,
        x: operand
      });
    } else if (name === "jmp") {
      if (tokens.length !== 3) bad(i + 1);

      const operand = parseOperand(tokens[1]);
      if (!operand) bad(i + 1);
      if (!isInteger(tokens[2])) bad(i + 1);

      instructions.push({
        op: name,
        x: operand,
        n: Number(tokens[2])
      });
    } else {
      bad(i + 1);
    }
  }

  const output = [];
  let ip = 0;
  let steps = 0;

  while (ip >= 0 && ip < instructions.length) {
    if (steps >= 10000) {
      throw new Error("step limit");
    }

    const instr = instructions[ip];
    steps++;

    if (instr.op === "set") {
      registers[instr.reg] = operandValue(instr.x);
      ip++;
    } else if (instr.op === "add") {
      registers[instr.reg] = (registers[instr.reg] + operandValue(instr.x)) % 1000;
      ip++;
    } else if (instr.op === "mul") {
      registers[instr.reg] = (registers[instr.reg] * operandValue(instr.x)) % 1000;
      ip++;
    } else if (instr.op === "out") {
      output.push(operandValue(instr.x));
      ip++;
    } else if (instr.op === "jmp") {
      if (operandValue(instr.x) !== 0) {
        ip += instr.n;
      } else {
        ip++;
      }
    }
  }

  return output;
}

module.exports = { runTik };
```