===== 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').map(line => line.trim());
  const output = [];
  let pc = 0;
  let step = 0;
  const registers = { a: 0, b: 0, c: 0, d: 0 };

  function normalize(value) {
    return value % 1000;
  }

  function isIntegerLiteral(s) {
    if (s === '') return false;
    if (s[0] === '-' || s[0] === '+') {
      return /^\-?\d+$/.test(s);
    }
    return /^\d+$/.test(s);
  }

  function parseLine(line) {
    if (line === '') return null;
    if (line.startsWith('#')) return null;

    const tokens = line.split(/\s+/).filter(t => t !== '');
    if (tokens.length === 0) return null;

    const op = tokens[0];
    const args = tokens.slice(1);

    if (op === 'set' && args.length === 2) {
      const r = args[0];
      const x = args[1];
      if (['a', 'b', 'c', 'd'].includes(r) && isIntegerLiteral(x)) {
        registers[r] = normalize(parseInt(x));
        return { type: 'set', r, x };
      }
    } else if (op === 'add' && args.length === 2) {
      const r = args[0];
      const x = args[1];
      if (['a', 'b', 'c', ''d'].includes(r) && isIntegerLiteral(x)) {
        registers[r] = normalize(registers[r] + parseInt(x));
        return { type: 'add', r, x };
      }
    } else if (op === 'mul' && args.length === 2) {
      const r = args[0];
      const x = args[1];
      if (['a', 'b', 'c', 'd'].includes(r) && isIntegerLiteral(x)) {
        registers[r] = normalize(registers[r] * parseInt(x));
        return { type: 'mul', r, x };
      }
    } else if (op === 'out' && args.length === 1) {
      const x = args[0];
      if (isIntegerLiteral(x)) {
        output.push(normalize(parseInt(x)));
        return { type: 'out', x };
      }
    } else if (op === 'jmp' && args.length === 2) {
      const x = args[0];
      const n = args[1];
      if (isIntegerLiteral(x) && isIntegerLiteral(n)) {
        const val = normalize(parseInt(x));
        if (val !== 0) {
          return { type: 'jmp', x, n };
        }
      }
    }

    return null;
  }

  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    const instr = parseLine(line);
    if (!instr) {
      continue;
    }

    if (step >= 10000) {
      throw new Error('step limit');
    }

    if (instr.type === 'jmp') {
      const val = normalize(parseInt(instr.x));
      const n = parseInt(instr.n);
      pc += val !== 0 ? n : 1;
    } else {
      pc++;
    }

    step++;
  }

  return output;
}
```