救我......

#include<bits/stdc++.h>
#define Inf 0x7fffffff
using namespace std;
queue<int> Q;
int Ht[9]= {0,-2,-2,-1,-1,1,1,2,2};
int Lt[9]= {0,1,-1,2,-2,2,-2,1,-1};
int a,b,x,X,Y,n,m,New,B,W,Black,White,Start,End,Cnt,Used,Ans,Head[40010],Cur[40010],Dep[40010],To[400010],Next[400010],Val[00010],Map[210][210],Id[210][210];
template<typename T>
int Read(T &x) {
	x=0;
	int f=1;
	char c=getchar();
	while(c!='-'&&!isdigit(c)) {
		c=getchar();
	}
	while(!isdigit(c)) {
		if(c=='-') {
			f=-f;
		}
		c=getchar();
	}
	while(isdigit(c)) {
		x=x*10+c-'0';
		c=getchar();
	}
	x*=f;
	if(c=='\n') {
		return 1;
	} else {
		return 0;
	}
}
void Write(long long x) {
	if(x<0) {
		putchar('-');
		x=-x;
	}
	if(x>9) {
		Write(x/10);
	}
	putchar(x%10+'0');
}
inline int Num(int x,int y) {
	return (x-1)*n+y;
}
inline void Add(int a,int b,int x) {
	To[++Cnt]=b;
	Next[Cnt]=Head[a];
	Head[a]=Cnt;
	Val[Cnt]=x;
	To[++Cnt]=a;
	Next[Cnt]=Head[b];
	Head[b]=Cnt;
	Val[Cnt]=0;
}
bool Bfs() {
	memset(Dep,-1,sizeof(Dep));
	Dep[Start]=0;
	Q.push(Start);
	while(!Q.empty()) {
		x=Q.front();
		Q.pop();
		for(int i=Head[x]; i; i=Next[i]) {
			if(Val[i]&&Dep[To[i]]==-1) {
				Dep[To[i]]=Dep[x]+1;
				Q.push(To[i]);
			}
		}
	}
	return Dep[End]!=-1;
}
int Dfs(int x,int f) {
	int w=0,Used=0;
	if(x==End) {
		return f;
	}
	for(int i=Cur[x]; i; i=Next[i]) {
		if(Dep[To[i]]==Dep[x]+1) {
			w=f-Used;
			w=Dfs(To[i],min(Val[i],w));
			Val[i]-=w;
			if(Val[i]) {
				Cur[x]=i;
			}
			Val[i^1]+=w;
			Used+=w;
			if(Used==f) {
				return f;
			}
		}
	}
	if(!Used) {
		Dep[x]=-1;
	}
	return Used;
}
void Dinic() {
	while(Bfs()) {
		for(int i=1; i<=n*n+5; i++) {
			Cur[i]=Head[i];
		}
		Ans+=Dfs(Start,Inf);
	}
}
int main() {
	Ans=0;
	Cnt=1;
	Read(n);
	Read(m);
	for(int i=1; i<=m; i++) {
		Read(X);
		Read(Y);
		Map[X][Y]=1;
	}
	Start=n*n+1;
	End=n*n+2;
	for(int i=1; i<=n; i++) {
		for(int j=1; j<=n; j++) {
			if(Map[i][j]) {
				continue;
			}
			if((i+j)&1) {
				Add(Start,Num(i,j),1);
				for(int k=1; k<=8; k++) {
					X=i+Ht[k];
					Y=j+Lt[k];
					if((X>n)||(X<1)||(Y<1)||(Y>n)||(Map[X][Y])) {
						continue;
					}
					Add(Num(i,j),Num(X,Y),Inf);
				}
			} 
			else {
				Add(Num(i,j),End,1);
			}
		}
	}
	Dinic();
	Write(n*n-Ans-m);
	return 0;
}