/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public int sumOfLeftLeaves(TreeNode root) {
    if(root == null) return 0;
    int ans = 0;
    if(root.left != null) {
        if(root.left.left == null && root.left.right == null) ans += root.left.val;
        else ans += sumOfLeftLeaves(root.left);
    }
    ans += sumOfLeftLeaves(root.right);
    
    return ans;
}