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#define ll long long
#define inf 0x3f3f3f3f
#define N 50000
using namespace std;
struct {
int dis,to,next;
}e[1000055];
inline int read(){
int x=0,w=0;char ch=getchar();
while (!isdigit(ch))w|=ch=='-',ch=getchar();
while (isdigit(ch))x=(x<<1)+(x<<3)+ch-'0',ch=getchar();
return w?-x:x;
}
int dx[]={-2,-2,-1,-1,1,1,2,2},dy[]={-1,1,-2,2,2,-2,-1,1},tot,id[207][207],ma[207][207],cnt=1,head[N],dep[N],inque[N],cur[N],n,m,s,t;
inline void add(int u,int v,int d){
e[++cnt].to=v;
e[cnt].dis=d;
e[cnt].next=head[u];
head[u]=cnt;
e[++cnt].to=u;
e[cnt].dis=0;
e[cnt].next=head[v];
head[v]=cnt;
}
bool bfs(){
memset(dep,0,sizeof(dep));
queue<int>q;q.push(s);dep[s]=1;
while (!q.empty()){
int u=q.front();q.pop();inque[u]=0;
for (int i=head[u];i;i=e[i].next){
int v=e[i].to;
if (!dep[v]&&e[i].dis){
dep[v]=dep[u]+1;
if (!inque[v])
q.push(v),inque[v]=1;
}
}
}
return dep[t];
}
int dfs(int u,int mn){
if (u==t)return mn;
int used=0,mi;
for (int &i=cur[u];i;i=e[i].next){
int v=e[i].to;
if (e[i].dis&&dep[v]==dep[u]+1)
if (mi=dfs(v,min(e[i].dis,mn-used))){
e[i].dis-=mi;
e[i^1].dis+=mi;
used+=mi;
if (used==mn)break;
}
}
return used;
}
int Dinic(){
int res=0;
while (bfs()){
for (int i=s;i<=t;++i)cur[i]=head[i];
res+=dfs(s,inf);
}
return res;
}
signed main(){
n=read(),m=read(),s=0,t=n*n-m+1;
for (int i=1;i<=m;++i)ma[read()][read()]=1;
for (int i=1;i<=n;++i)
for (int j=1;j<=n;++j)
if (!ma[i][j]){
id[i][j]=++tot;
if ((i+j)&1)add(s,id[i][j],1);
else add(id[i][j],t,1);
}
for (int i=1;i<=n;++i)
for (int j=1;j<=n;++j)
if (!ma[i][j]){
for (int p=0;p<8;++p){
int x=i+dx[p],y=j+dy[p];
if (ma[x][y]||x<1||y<1||x>n||y>n)continue;
if ((i+j)&1)
add(id[i][j],id[x][y],1);
else add(id[x][y],id[i][j],1);
}
}
printf("%dn",n*n-m-Dinic());
}
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