===== 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 stepCount = 0;
  const registers = { a: 0, b: 0, c: 0, d: 0 };

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

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

  function parseLiteral(str) {
    if (str[0] === '-' || str[0] === '+') {
      return normalize(parseInt(str, 10));
    }
    return normalize(parseInt(str, 10));
  }

  function isValidRegister(name) {
    return ['a', 'b', 'c', 'd'].includes(name);
  }

  function isValidInstruction(line, lineNumber) {
    if (line === '') return false;
    if (line.startsWith('#')) return false;
    const parts = line.split(/\s+/);
    if (parts.length < 2) return false;
    const op = parts[0];
    const args = parts.slice(1);

    switch (op) {
      case 'set':
        if (args.length !== 2) return false;
        if (!isValidRegister(args[0])) return false;
        if (!isValidLiteral(args[1])) return false;
        return true;
      case 'add':
        if (args.length !== 2) return false;
        if (!isValidRegister(args[0])) return false;
        if (!isValidLiteral(args[1])) return
```