#include <bits/stdc++.h>
using namespace std;
long long int sett(long long int N, int pos) { return N = N | (1 << pos); }
int reset(int N, int pos) { return N = N & ~(1 << pos); }
bool check(int N, int pos) { return (bool)(N & (1 << pos)); }
void update(long long &x, long long val) {
  x = x + val;
  if (x > 1000000007) x -= 1000000007;
}
void fast() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL), cout.tie(NULL);
}
int moves[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
int main() {
  int n;
  cin >> n;
  int row[n];
  int col[n];
  memset(row, 0, sizeof(row));
  memset(col, 0, sizeof(col));
  int p;
  cin >> p;
  for (int i = 0; i < p; i++) {
    int a, b;
    scanf("%d%d", &a, &b);
    row[a - 1] = 1;
    col[b - 1] = 1;
  }
  int ans = n * 2 - 4;
  for (int i = 1; i < n - 1; i++) {
    if (row[i]) {
      ans--;
    }
    if (col[i]) {
      ans--;
    }
  }
  if (n % 2 == 1) {
    if (row[n / 2] != 1 && col[n / 2] != 1) ans--;
  }
  cout << ans;
  return 0;
}
