Problem Statement

There are $N$ turkeys. We number them from $1$ through $N$.

$M$ men will visit here one by one. The $i$-th man to visit will take the following action:

• If both turkeys $x_i$ and $y_i$ are alive: selects one of them with equal probability, then eats it.
• If either turkey $x_i$ or $y_i$ is alive (but not both): eats the alive one.
• If neither turkey $x_i$ nor $y_i$ is alive: does nothing.

Find the number of pairs $(i,\ j)$ ($1 ≤ i < j ≤ N$) such that the following condition is held:

• The probability of both turkeys $i$ and $j$ being alive after all the men took actions, is greater than $0$.

Constraints

• $2 ≤ N ≤ 400$
• $1 ≤ M ≤ 10^5$
• $1 ≤ x_i < y_i ≤ N$

Input

Input is given from Standard Input in the following format:

N M
x_1 y_1
x_2 y_2
:
x_M y_M

Output

Print the number of pairs $(i,\ j)$ ($1 ≤ i < j ≤ N$) such that the condition is held.