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const map = 'abcdefghijklmnopqrstuvwxyz';

function getSymbol(value, charMap) {
  const charArray = charMap.split('');
  const charLength = charArray.length;
  let factors = [1];
  let charReturn = [];
  // bump value by 1 so that value of 0 == a but 26 == aa
  let remainder = value + 1; 
  if (charLength < 2 || value < 0) {
    return null;
  // find all the factors of map length that goes into value
  for (let i = charLength; i <= value; i = i * charLength) {
  // starting with largest factor, find how many times each factor goes into value, then repeat on remainder
  for (factor of factors.reverse()) {
    const digit = Math.floor(remainder / factor); 
    remainder = remainder % factor;
  return charReturn.join('');;

console.log(getSymbol(0, map));
console.log(getSymbol(25, map));
console.log(getSymbol(26, map));
console.log(getSymbol(2367368, map));