function substrCount(n, s) {
  let _specials = 0;

  const charr = [...s];
  for (let i = 0; i < n; i++) {
    let specialChar = charr[i];
    let nextCharIdx = i + 1;

    let isSpecial = true;
    while (isSpecial) {
      const nextChar = charr[nextCharIdx];

      if (!nextChar) break; // eol

      // check if same char => special (e.g. 'aa' or 'aaa')
      if (nextChar === specialChar) {
        _specials++;
        nextCharIdx++;
      } else {
        // check for substring with 'special middle char' (e.g. 'aabaa')
        const length = nextCharIdx - i;
        if (nextCharIdx + 1 + length <= n) { // check eol
          const afterStr = s.substring(nextCharIdx + 1, nextCharIdx + 1 + length);
          if ([...afterStr].every((c) => c === specialChar)) {
            _specials++;
          }
        }
        isSpecial = false;
      }
    }
  }

  return _specials + n;
}