function flags(a: number[]): number {
  const size = a.length;
  const peaks: boolean[] = [false];
  const next: number[] = [];

  for (let i = 1; i < size; i++) {
    peaks[i] = a[i - 1] < a[i] && a[i] > (a[i + 1] ?? 0);
  }

  next[size - 1] = -1;
  for (let i = size - 2; i >= 0; i--) {
    next[i] = peaks[i] ? i : next[i + 1];
  }

  let i = 1;
  let result = 0;
  while (i * (i - 1) <= size) {
    let pos = 0;
    let num = 0;
    while (pos < size && num < i) {
      pos = next[pos];
      if (pos === -1) {
        break;
      }
      ++num;
      pos += i;
    }
    i++;
    result = Math.max(result, num);
  }

  return result;
}