Score : 600 points

Problem Statement

We have a tree with N vertices and N-1 edges, respectively numbered 1, 2,\cdots, N and 1, 2, \cdots, N-1. Edge i connects Vertex u_i and v_i.

For integers L, R (1 \leq L \leq R \leq N), let us define a function f(L, R) as follows:

Let S be the set of the vertices numbered L through R. f(L, R) represents the number of connected components in the subgraph formed only from the vertex set S and the edges whose endpoints both belong to S.

Compute \sum_{L=1}^{N} \sum_{R=L}^{N} f(L, R).

Constraints

1 \leq N \leq 2 \times 10^5
1 \leq u_i, v_i \leq N
The given graph is a tree.
All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
u_1 v_1
u_2 v_2
:
u_{N-1} v_{N-1}

Output

Print \sum_{L=1}^{N} \sum_{R=L}^{N} f(L, R).

Sample Input 1

3
1 3
2 3

Sample Output 1

We have six possible pairs (L, R) as follows:

For L = 1, R = 1, S = \{1\} and we have 1 connected component.
For L = 1, R = 2, S = \{1, 2\} and we have 2 connected components.
For L = 1, R = 3, S = \{1, 2, 3\} and we have 1 connected component, since S contains both endpoints of each of the edges 1, 2.
For L = 2, R = 2, S = \{2\} and we have 1 connected component.
For L = 2, R = 3, S = \{2, 3\} and we have 1 connected component, since S contains both endpoints of Edge 2.
For L = 3, R = 3, S = \{3\} and we have 1 connected component.

The sum of these is 7.

Sample Input 2

2
1 2

Sample Output 2

Sample Input 3