Problem Statement

You are given N intervals of real numbers. The $i-th (1 \leq i \leq N)$ interval is [l_i, r_i]. Find the number of pairs (i, j)$,(1 \leq i < j \leq N)$ such that the i-th and j-th intervals intersect.

Input

The input is given from Standard Input in the following format:
N
l_1 r_1
l_2 r_2
$\vdots$
l_N r_N

Output

Print the answer.

Constraints

• $2 \leq N \leq 5 \times 10^5$
• $0 \leq l_i < r_i \leq 10^9$
• All input values are integers.

Sample Input 1

3
1 5
7 8
3 7

Sample Output 1

2

The given intervals are [1,5], [7,8], [3,7]. Among these, the 1-st and 3-rd intervals intersect, as well as the 2-nd and 3-rd intervals, so the answer is 2.

Sample Input 2

3
3 4
2 5
1 6

Sample Output 2

3

Sample Input 3

2
1 2
3 4

Sample Output 3

0

见题面 Input 部分

见题面 Output 部分