#include <bits/stdc++.h>
using namespace std;
bool r[1010], c[1010];
int main() {
  int n, m, x, y, i, j;
  scanf("%d", &n);
  scanf("%d", &m);
  for (i = 1; i <= n - 2; i++) r[i] = c[i] = 1;
  for (i = 0; i < m; ++i) {
    scanf("%d", &x);
    scanf("%d", &y);
    --x;
    --y;
    r[x] = c[y] = 0;
  }
  int ans = 0;
  for (i = 1; n - 1 - i > i; i++) {
    int maxx = 0;
    for (j = 0; j < 81; ++j) {
      int r1, r2, c1, c2, j1 = j;
      r1 = j1 % 3;
      j1 /= 3;
      r2 = j1 % 3;
      j1 /= 3;
      c1 = j1 % 3;
      j1 /= 3;
      c2 = j1;
      if (r[i] == 0 && r1 > 0) continue;
      if (r[n - 1 - i] == 0 && r2 > 0) continue;
      if (c[i] == 0 && c1 > 0) continue;
      if (c[n - 1 - i] == 0 && c2 > 0) continue;
      if ((r1 == c1 && r1) || (r1 != c2 && r1 && c2)) continue;
      if ((r2 == c2 && r2) || (r2 != c1 && r2 && c1)) continue;
      int cnt = 0;
      if (r1) cnt++;
      if (r2) cnt++;
      if (c1) cnt++;
      if (c2) cnt++;
      maxx = max(maxx, cnt);
    }
    ans = ans + maxx;
  }
  if (n % 2 == 1) {
    if (c[n / 2] || r[n / 2]) ans++;
  }
  printf("%d\n", ans);
}
