#include <bits/stdc++.h>
using namespace std;
using pii = pair<int, int>;
const int N = 1000;
int n, m, ans;
bool a[N + 1][N + 1];
bool good(int i, bool row) {
  for (int j = 1; j <= n; j++) {
    if (row ? a[i][j] : a[j][i]) return false;
  }
  return true;
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout << fixed;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int x, y;
    cin >> x >> y;
    a[x][y] = true;
  }
  for (int i = 2; i <= n + 1 - i; i++) {
    int j = n + 1 - i;
    if (i == j) {
      ans += good(i, true) || good(i, false);
    } else {
      ans += good(i, true) + good(j, false) + good(j, true) + good(i, false);
    }
  }
  cout << ans << endl;
  return 0;
}
