p03691 AtCoder Grand Contest 016 - Poor Turkeys
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.

Examples

Input

3 1
1 2


Output

2


Input

4 3
1 2
3 4
2 3


Output

1


Input

3 2
1 2
1 2


Output

0


Input

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


Output

5
```python
import sys

from itertools import combinations


def solve(n, pairs):
    survivors = {v: {v} for v in range(1, n + 1)}
    for x, y in reversed(pairs):
        for v, srv in survivors.copy().items():
            if x in srv:
                if y in srv:
                    del survivors[v]
                else:
                    srv.add(y)
            elif y in srv:
                srv.add(x)
    return sum(su.isdisjoint(sv) for su, sv in combinations(survivors.values(), 2))


n, m = map(int, input().split())
pairs = [tuple(map(int, line.split())) for line in sys.stdin.readlines()]
print(solve(n, pairs))

```