write a go solution for Description:
Turtle just received n segments and a sequence a_1,a_2,ldots,a_n. The i-th segment is [l_i,r_i].

Turtle will create an undirected graph G. If segment i and segment j intersect, then Turtle will add an undirected edge between i and j with a weight of |a_i-a_j|, for every inej.

Turtle wants you to calculate the sum of the weights of the edges of the minimum spanning tree of the graph G, or report that the graph G has no spanning tree.

We say two segments [l_1,r_1] and [l_2,r_2] intersect if and only if max(l_1,l_2)<=min(r_1,r_2).

Input Format:
Each test contains multiple test cases. The first line contains the number of test cases t (1<=t<=10^5). The description of the test cases follows.

The first line of each test case contains a single integer n (2<=n<=5*10^5) — the number of segments.

The i-th of the following n lines contains three integers l_i,r_i,a_i (1<=l_i<=r_i<=10^9,1<=a_i<=10^9) — the i-th segment and the i-th element of the sequence.

It is guaranteed that the sum of n over all test cases does not exceed 5*10^5.

Output Format:
For each test case, output a single integer — the sum of the weights of the edges of the minimum spanning tree of the graph G. If the graph G has no spanning tree, output -1.

Note:
In the first test case, the graph G is as follows:

One of the minimum spanning trees of G is as follows:

The sum of the weights of the edges of the minimum spanning tree is 9.

In the second test case, the graph G is as follows:

G is already a tree, and the sum of the weights of the tree is 13.

In the third test case, the graph G is as follows:

In the fourth test case, the graph G is as follows:

It's easy to see that G is not connected, so G has no spanning tree.. Output only the code with no comments, explanation, or additional text.