//It is made by wfj_2048~
#include <algorithm>
#include <iostream>
#include <complex>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <vector>
#include <cmath>
#include <queue>
#include <stack>
#include <map>
#include <set>
#define inf (1<<30)
#define il inline
#define RG register
#define ll long long
#define c(i,j) ( (i-1)*n+j )
#define File(s) freopen(s".in","r",stdin),freopen(s".out","w",stdout)

using namespace std;

struct edge{ int nt,to,flow,cap; }g[5000010];

int head[100010],d[100010],q[100010],a[310][310],vi[310][310],n,m,S,T,num=1;

il int gi(){
    RG int x=0,q=1; RG char ch=getchar(); while ((ch<‘0‘ || ch>‘9‘) && ch!=‘-‘) ch=getchar();
    if (ch==‘-‘) q=-1,ch=getchar(); while (ch>=‘0‘ && ch<=‘9‘) x=x*10+ch-48,ch=getchar(); return q*x;
}

il void insert(RG int from,RG int to,RG int cap){ g[++num]=(edge){head[from],to,0,cap},head[from]=num; return; }

il int bfs(RG int S,RG int T){
    memset(d,0,sizeof(d)); RG int h=0,t=1; q[t]=S,d[S]=1;
    while (h<t){
    RG int x=q[++h];
    for (RG int i=head[x];i;i=g[i].nt){
        RG int v=g[i].to;
        if (!d[v] && g[i].cap>g[i].flow){
        q[++t]=v,d[v]=d[x]+1;
        if (v==T) return 1;
        }
    }
    }
    return 0;
}

il int dfs(RG int x,RG int T,RG int a){
    if (x==T || !a) return a; RG int f,flow=0;
    for (RG int i=head[x];i;i=g[i].nt){
    RG int v=g[i].to;
    if (d[v]==d[x]+1 && g[i].cap>g[i].flow){
        f=dfs(v,T,min(a,g[i].cap-g[i].flow));
        if (!f){ d[v]=-1; continue; }
        g[i].flow+=f,g[i^1].flow-=f;
        flow+=f,a-=f; if (!a) return flow;
    }
    }
    return flow;
}

il int maxflow(RG int S,RG int T){ RG int flow=0; while (bfs(S,T)) flow+=dfs(S,T,inf); return flow; }

il void work(){
    n=gi(),m=gi(); RG int x,y; S=n*n+1,T=n*n+2;
    for (RG int i=1;i<=m;++i) x=gi(),y=gi(),vi[x][y]=1;
    for (RG int i=1;i<=n;++i) for (RG int j=1;j<=n;++j) if ((i+j)&1) a[i][j]=1;
    for (RG int i=1;i<=n;++i)
    for (RG int j=1;j<=n;++j)
        if (!a[i][j]){ if (!vi[i][j]) insert(c(i,j),T,1),insert(T,c(i,j),0); } else{
        if (vi[i][j]) continue; insert(S,c(i,j),1),insert(c(i,j),S,0);
        if (i>=3 && j>=2 && !vi[i-2][j-1]) insert(c(i,j),c(i-2,j-1),inf),insert(c(i-2,j-1),c(i,j),0);
        if (i>=2 && j>=3 && !vi[i-1][j-2]) insert(c(i,j),c(i-1,j-2),inf),insert(c(i-1,j-2),c(i,j),0);
        if (i>=3 && j+1<=n && !vi[i-2][j+1]) insert(c(i,j),c(i-2,j+1),inf),insert(c(i-2,j+1),c(i,j),0);
        if (i>=2 && j+2<=n && !vi[i-1][j+2]) insert(c(i,j),c(i-1,j+2),inf),insert(c(i-1,j+2),c(i,j),0);
        if (i+2<=n && j>=2 && !vi[i+2][j-1]) insert(c(i,j),c(i+2,j-1),inf),insert(c(i+2,j-1),c(i,j),0);
        if (i+1<=n && j>=3 && !vi[i+1][j-2]) insert(c(i,j),c(i+1,j-2),inf),insert(c(i+1,j-2),c(i,j),0);
        if (i+2<=n && j+1<=n && !vi[i+2][j+1]) insert(c(i,j),c(i+2,j+1),inf),insert(c(i+2,j+1),c(i,j),0);
        if (i+1<=n && j+2<=n && !vi[i+1][j+2]) insert(c(i,j),c(i+1,j+2),inf),insert(c(i+1,j+2),c(i,j),0);
        }
    printf("%d\n",n*n-m-maxflow(S,T)); return;
}

int main(){
    File("knight");
    work();
    return 0;
}