Thank you : )

```
public class Solution {
public int sumOfLeftLeaves(TreeNode root) {
if (root == null)
return 0;
int sum = 0;
if (root.left != null || root.right != null) {
sum = sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
}
if (root.left != null && root.left.left == null && root.left.right == null)
sum = sum + root.left.val;
return sum;
}
}
```