#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  int x, y;
  bool r[1010], c[1010];
  bool user[1010], usec[1010];
  cin >> n >> m;
  for (int i = 0; i < (int)(n); i++) r[i] = c[i] = user[i] = usec[i] = false;
  r[0] = r[n - 1] = c[0] = c[n - 1] = true;
  for (int i = 0; i < (int)(m); i++) {
    cin >> x >> y;
    r[y - 1] = c[x - 1] = true;
  }
  int ans = 0;
  for (int i = 0; i < (int)(n / 2); i++) {
    if (!r[i]) ans++;
    if (!r[n - 1 - i]) ans++;
    if (!c[i]) ans++;
    if (!c[n - 1 - i]) ans++;
  }
  if (n & 1 && (!r[n / 2] || !c[n / 2])) ans++;
  cout << ans << endl;
}
