You are given pointer to the root of the binary search tree and two values and . You need to return the lowest common ancestor (LCA) of and in the binary search tree.

In the diagram above, the lowest common ancestor of the nodes and is the node . Node is the lowest node which has nodes and as descendants.

**Function Description**

Complete the function *lca* in the editor below. It should return a pointer to the lowest common ancestor node of the two values given.

lca has the following parameters:

- root: a pointer to the root node of a binary search tree

- v1: a node.data value

- v2: a node.data value

**Input Format**

The first line contains an integer, , the number of nodes in the tree.

The second line contains space-separated integers representing values.

The third line contains two space-separated integers, and .

To use the test data, you will have to create the binary search tree yourself. Here on the platform, the tree will be created for you.

**Constraints**

The tree will contain nodes with *data* equal to and .

**Output Format**

Return the a pointer to the node that is the lowest common ancestor of and .

**Sample Input**

```
6
4 2 3 1 7 6
1 7
```

and .

**Sample Output**

[reference to node 4]

**Explanation**

LCA of and is , the root in this case.

Return a pointer to the node.