#include <bits/stdc++.h>
using namespace std;
const long long N = 1000 + 5, K = 21, mod = 998244353, MOD = 998244353;
void solve() {
  long long n, m;
  cin >> n >> m;
  vector<long long> row(n + 1), col(n + 1);
  long long x, y;
  for (long long i = 0; i < m; i++) {
    cin >> x >> y;
    row[x] = 1;
    col[y] = 1;
  }
  long long ans = 0;
  for (long long i = 2; i <= (n + 1) / 2; i++) {
    if (i == n - i + 1) {
      if (!row[i] || !col[i]) ans++;
      continue;
    }
    if (!row[i]) ans++;
    if (!col[n - i + 1]) ans++;
    if (!row[n - i + 1]) ans++;
    if (!col[i]) ans++;
  }
  cout << ans << endl;
}
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long TESTS = 1;
  while (TESTS--) {
    solve();
  }
  return 0;
}
