❔ ✅ Missing a first element of the output

public class Solution {
    public IList<int> Preorder(Node root) {
        List<int> ans = new List<int>();
        if(root == null){
            return ans;
        }
        Helper(root, ans);
        return ans;
        
    }

    public void Helper(Node root, List<int> ans){
        foreach(var node in root.children){
            
            ans.Add(node.val);
            Helper(node, ans);
        }
    }
}