#include <bits/stdc++.h>
bool x[1001], y[1001];
int n, m;
int main() {
  int i, ans, a, b;
  scanf("%d%d", &n, &m);
  memset(x, true, sizeof(x));
  memset(y, true, sizeof(y));
  for (i = 1; i <= m; i++) {
    scanf("%d%d", &a, &b);
    x[a] = false;
    y[b] = false;
  }
  ans = 0;
  for (i = 2; i <= n / 2; i++) {
    if (x[i]) ans++;
    if (x[n - i + 1]) ans++;
    if (y[i]) ans++;
    if (y[n - i + 1]) ans++;
  }
  if (n % 2 == 1)
    if (x[(n + 1) / 2] || y[(n + 1) / 2]) ans++;
  printf("%d\n", ans);
  return 0;
}
