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

#include <cstdio>
#include <cstddef>

bool dead[400][400];

int main() {
  size_t N, M;
  std::scanf(" %zu %zu", &N, &M);
  while (M--) {
    size_t u, v;
    std::scanf(" %zu %zu", &u, &v);
    --u; --v;
    if (!dead[u][v]) {
      dead[u][v] = dead[v][u] = true;
      for (size_t w = 0; w < N; ++w) {
        if (dead[u][w]) {
          dead[v][w] = dead[w][v] = true;
        }
      }
      for (size_t w = 0; w < N; ++w) {
        if (dead[v][w]) {
          dead[u][w] = dead[w][u] = true;
        }
      }
    }
    else {
      for (size_t w = 0; w < N; ++w) {
        dead[u][w] = dead[w][u] = dead[v][w] = dead[w][v] = true;
      }
    }
  }
  size_t ans = 0;
  for (size_t u = 0; u < N; ++u) {
    for (size_t v = 0; v < u; ++v) {
      if (!dead[u][v]) {
        ++ans;
      }
    }
  }
  std::printf("%zu\n", ans);
  return 0;
}
