#include <bits/stdc++.h>
using namespace std;
int br[1001];
int bc[1001];
int main() {
  int n, m;
  cin >> n >> m;
  int bx, by;
  for (int i = 0; i < m; i++) {
    cin >> bx >> by;
    br[bx]++;
    bc[by]++;
  }
  int ans = 0;
  for (int i = 2; i <= n / 2; i++) {
    if (br[i] == 0) ans++;
    if (br[n - i + 1] == 0) ans++;
    if (bc[i] == 0) ans++;
    if (bc[n - i + 1] == 0) ans++;
  }
  if (n & 1) {
    if (br[(n + 1) / 2] == 0 || bc[(n + 1) / 2] == 0) ans++;
  }
  cout << ans;
  return 0;
}
