func findMaxLength(nums []int) int {
	n := len(nums)
	if n < 2 {
		return 0
	}
	dp := make([]int, n+1)
	for i := range nums {
		if nums[i] == 0 {
			dp[i+1] = dp[i]
		} else {
			dp[i+1] = dp[i] + 1
		}
	}
	for l := n / 2 * 2; 2 <= l; l -= 2 {
		for i := n; 0 <= i-l; i-- { // On^2
			if dp[i]-dp[i-l] == l/2 {
				return l
			}
		}
	}
	return 0
}