13B. Crossfire Friends

There are $2n$ musketeers standing on a coordinate grid.

For each $i$ with $1 \le i \le n$, one musketeer stands at $(0, i)$ and shoots a bullet parallel to the positive direction of the $x$-axis.

For each $i$ with $1 \le i \le n$, one musketeer stands at $(i, 0)$ and shoots a bullet parallel to the positive direction of the $y$-axis.

All bullets are shot at the same time. The speed of the bullet shot from $(0, i)$ is $h_i$ units per second, and the speed of the bullet shot from $(i, 0)$ is $v_i$ units per second.

Bullets pass through each other and continue moving. If at some real time $t$ with $0 \le t \le n$ two bullets are at the same point, the two musketeers who shot them become friends.

For each test case, find the number of pairs of musketeers that become friends.