#include <bits/stdc++.h>
using namespace std;
const int N = 1001;
bool rows[N], cols[N];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < m; ++i) {
    int x, y;
    cin >> x >> y;
    rows[x] = cols[y] = 1;
  }
  int ans = 0;
  for (int i = 2; 2 * i <= n; ++i) {
    ans += 4 - (rows[i] + rows[n - i + 1] + cols[i] + cols[n - i + 1]);
  }
  if (n % 2) ans += (!rows[n / 2 + 1] || !cols[n / 2 + 1]);
  cout << ans << '\n';
}
