Package for this problem was not updated by the problem writer or Codeforces administration after we’ve upgraded the judging servers. To adjust the time limit constraint, solution execution time will be multiplied by 2. For example, if your solution works for 400 ms on judging servers, then value 800 ms will be displayed and used to determine the verdict.

Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ACM-ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

A. Games

time limit per test

1 secondmemory limit per test

256 megabytesinput

standard inputoutput

standard outputManao works on a sports TV. He's spent much time watching the football games of some country. After a while he began to notice different patterns. For example, each team has two sets of uniforms: home uniform and guest uniform. When a team plays a game at home, the players put on the home uniform. When a team plays as a guest on somebody else's stadium, the players put on the guest uniform. The only exception to that rule is: when the home uniform color of the host team matches the guests' uniform, the host team puts on its guest uniform as well. For each team the color of the home and guest uniform is different.

There are *n* teams taking part in the national championship. The championship consists of *n*·(*n* - 1) games: each team invites each other team to its stadium. At this point Manao wondered: how many times during the championship is a host team going to put on the guest uniform? Note that the order of the games does not affect this number.

You know the colors of the home and guest uniform for each team. For simplicity, the colors are numbered by integers in such a way that no two distinct colors have the same number. Help Manao find the answer to his question.

Input

The first line contains an integer *n* (2 ≤ *n* ≤ 30). Each of the following *n* lines contains a pair of distinct space-separated integers *h*_{i}, *a*_{i} (1 ≤ *h*_{i}, *a*_{i} ≤ 100) — the colors of the *i*-th team's home and guest uniforms, respectively.

Output

In a single line print the number of games where the host team is going to play in the guest uniform.

Examples

Input

3

1 2

2 4

3 4

Output

1

Input

4

100 42

42 100

5 42

100 5

Output

5

Input

2

1 2

1 2

Output

0

Note

In the first test case the championship consists of 6 games. The only game with the event in question is the game between teams 2 and 1 on the stadium of team 2.

In the second test sample the host team will have to wear guest uniform in the games between teams: 1 and 2, 2 and 1, 2 and 3, 3 and 4, 4 and 2 (the host team is written first).

Codeforces (c) Copyright 2010-2019 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Jul/18/2019 04:37:51 (g1).

Desktop version, switch to mobile version.

Supported by

User lists

Name |
---|