Problem Statement

There are $N wizards, numbered 1, \ldots, N$.
Wizard i has a strength of a_i and plans to defeat a monster with a strength of b_i.
You can perform the following operation any number of times.

• Increase the strength of any wizard of your choice by 1.

A pair of Wizard i and Wizard j (let us call this pair (i, j)) is said to be good when at least one of the following conditions is satisfied.

• Wizard i has a strength of at least b_i and Wizard j has a strength of at least b_j.
• Wizard i has a strength of at least b_j and Wizard j has a strength of at least b_i.

Your objective is to make the pair (x_i, y_i) good for every $i=1, \ldots, M$.
Find the minimum number of operations needed to achieve it.

Input

Input is given from Standard Input in the following format:
N
a_1 b_1
$\vdots$
a_N b_N
M
x_1 y_1
$\vdots$
x_M y_M

Output

Print the answer.

Constraints

• $2 \leq N \leq 100$
• $1 \leq a_i,b_i \leq 100$
• $1 \leq M \leq \frac{N(N-1)}{2}$
• $1 \leq x_i \lt y_i \leq N$
• $(x_i,y_i) \neq (x_j,y_j)$, if $i\neq j$.
• All values in input are integers.

Sample Input 1

5
1 5
2 4
3 3
4 2
5 1
3
1 4
2 5
3 5

Sample Output 1

2

You can perform the operation once for Wizard 1 and once for Wizard 4 to achieve the objective with the fewest operations.

Sample Input 2

4
1 1
1 1
1 1
1 1
3
1 2
2 3
3 4

Sample Output 2

0

No operation is needed.

Sample Input 3

9
1 1
2 4
5 5
7 10
9 3
9 13
10 9
3 9
2 9
7
1 5
2 5
1 6
2 4
3 4
4 9
8 9

Sample Output 3

22

见题面 Input 部分

见题面 Output 部分