#include <bits/stdc++.h>
using namespace std;
const int maxn = 1005;
bool col[maxn], row[maxn];
int main() {
  int n, m, a, b, ans;
  scanf("%d%d", &n, &m);
  memset(row, true, sizeof(row));
  memset(col, true, sizeof(col));
  if (n & 1)
    ans = (n - 3) * 2 + 1;
  else
    ans = (n - 2) * 2;
  while (m--) {
    scanf("%d%d", &a, &b);
    if (row[a] && a > 1 && a < n) {
      if (a != n - a + 1) ans--;
      row[a] = false;
    }
    if (col[b] && b > 1 && b < n) {
      if (b != n - b + 1) ans--;
      col[b] = false;
    }
  }
  if (n & 1 && !row[n / 2 + 1] && !col[n / 2 + 1]) ans--;
  printf("%d\n", ans);
  return 0;
}
