func flags(a []int) int {
	size := len(a)

	peaks := make([]bool, size)
	for i := 1; i < size; i++ {
		nextVal := 0
		if i+1 < size {
			nextVal = a[i+1]
		}
		peaks[i] = a[i-1] < a[i] && a[i] > nextVal
	}

	next := make([]int, size)
	next[size-1] = -1
	for i := size - 2; i >= 0; i-- {
		if peaks[i] {
			next[i] = i
		} else {
			next[i] = next[i+1]
		}
	}

	result := 0
	for i := 1; i*(i-1) <= size; i++ {
		pos, num := 0, 0
		for pos < size && num < i {
			pos = next[pos]
			if pos == -1 {
				break
			}
			num++
			pos += i
		}
		if num > result {
			result = num
		}
	}

	return result
}