Kamil and Making a Stream

Kamil likes streaming the competitive programming videos. His MeTube channel has recently reached $$$100$$$ million subscribers. In order to celebrate this, he posted a video with an interesting problem he couldn't solve yet. Can you help him?

You're given a tree — a connected undirected graph consisting of $$$n$$$ vertices connected by $$$n - 1$$$ edges. The tree is rooted at vertex $$$1$$$. A vertex $$$u$$$ is called an ancestor of $$$v$$$ if it lies on the shortest path between the root and $$$v$$$. In particular, a vertex is an ancestor of itself.

Each vertex $$$v$$$ is assigned its beauty $$$x_v$$$ — a non-negative integer not larger than $$$10^{12}$$$. This allows us to define the beauty of a path. Let $$$u$$$ be an ancestor of $$$v$$$. Then we define the beauty $$$f(u, v)$$$ as the greatest common divisor of the beauties of all vertices on the shortest path between $$$u$$$ and $$$v$$$. Formally, if $$$u=t_1, t_2, t_3, \dots, t_k=v$$$ are the vertices on the shortest path between $$$u$$$ and $$$v$$$, then $$$f(u, v) = \gcd(x_{t_1}, x_{t_2}, \dots, x_{t_k})$$$. Here, $$$\gcd$$$ denotes the greatest common divisor of a set of numbers. In particular, $$$f(u, u) = \gcd(x_u) = x_u$$$.

Your task is to find the sum

$$$$$$ \sum_{u\text{ is an ancestor of }v} f(u, v). $$$$$$

As the result might be too large, please output it modulo $$$10^9 + 7$$$.

Note that for each $$$y$$$, $$$\gcd(0, y) = \gcd(y, 0) = y$$$. In particular, $$$\gcd(0, 0) = 0$$$.