/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    public int MaxLevelSum(TreeNode root) {
        var level = 1;
        var max = int.MinValue;
        var minLevel = -1;
        
        var queue = new Queue<TreeNode>();
        queue.Enqueue(root);
        
        while(queue.Count > 0)
        {
            var size = queue.Count;
            var sum = 0;
            
            for(var i = 0; i<size; i++)
            {
                var current = queue.Dequeue();
                sum += current.val;
                
                if(current.left != null)
                    queue.Enqueue(current.left);
                
                if(current.right != null)
                    queue.Enqueue(current.right);
            }
            
            if(sum > max)
            {
                max = sum;
                minLevel = level;
            }
            
            level++;
        }
        
        return minLevel;
    }
}