#include <bits/stdc++.h>
using namespace std;
bool badX[1111];
bool badY[1111];
int main() {
  long long n, m, ans = 0;
  cin >> n >> m;
  int x, y;
  for (int i = 0; i < m; i++) {
    cin >> x >> y;
    badX[x] = true;
    badY[y] = true;
  }
  for (int i = 2; i <= n / 2; i++) {
    if (badX[i] == false) ans++;
    if (badY[i] == false) ans++;
    if (badX[n + 1 - i] == false) ans++;
    if (badY[n + 1 - i] == false) ans++;
  }
  if (n % 2 == 1)
    if ((badX[n / 2 + 1] == false) || (badY[n / 2 + 1] == false)) ans++;
  cout << ans;
  return 0;
}
