void dfs(int u, int w)
{
	if (u == 2) {
		res = lcm(res, w);
		return;
	}
	if (res % w == 0) //重要剪枝
		return;
	for (L * tmp = adj[u].next; tmp; tmp = tmp->next) {
		if (vis[tmp->v] == 0) {
			LL g = gcd(w, tmp->w);
			vis[tmp->v] = 1;
			if (g > 1 && res % g != 0) {
				dfs(tmp->v,g);
			}
			vis[tmp->v] = 0;
		}
	}
}