===== 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 lines = program.split('\n');
  const isReg = s => s === 'a' || s === 'b' || s === 'c' || s === 'd';
  const isLit = s => /^-?\d+$/.test(s);
  const isOperand = s => isReg(s) || isLit(s);

  const instrs = [];
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i].trim();
    if (line === '' || line[0] === '#') continue;
    const tokens = line.split(/ +/);
    const name = tokens[0];
    let valid = false;
    if (name === 'set' || name === 'add' || name === 'mul') {
      valid = tokens.length === 3 && isReg(tokens[1]) && isOperand(tokens[2]);
    } else if (name === 'out') {
      valid = tokens.length === 2 && isOperand(tokens[1]);
    } else if (name === 'jmp') {
      valid = tokens.length === 3 && isOperand(tokens[1]) && isLit(tokens[2]);
    }
    if (!valid) throw new Error('bad instruction at line ' + (i + 1));
    instrs.push(tokens);
  }

  const mod = n => ((n % 1000) + 1000) % 1000;
  const regs = { a: 0, b: 0, c: 0, d: 0 };
  const val = x => isReg(x) ? regs[x] : mod(parseInt(x, 10));

  const output = [];
  let pc = 0;
  let steps = 0;
  while (pc >= 0 && pc < instrs.length) {
    if (steps >= 10000) throw new Error('step limit');
    steps++;
    const t = instrs[pc];
    const name = t[0];
    if (name === 'set') {
      regs[t[1]] = val(t[2]);
      pc++;
    } else if (name === 'add') {
      regs[t[1]] = mod(regs[t[1]] + val(t[2]));
      pc++;
    } else if (name === 'mul') {
      regs[t[1]] = mod(regs[t[1]] * val(t[2]));
      pc++;
    } else if (name === 'out') {
      output.push(val(t[1]));
      pc++;
    } else { // jmp
      if (val(t[1]) !== 0) pc += parseInt(t[2], 10);
      else pc++;
    }
  }
  return output;
}

module.exports = { runTik };
```