大佬们的代码小于100ms，而同样是网络流的我写的$dinic$却有极大的常数，跑到了500ms，求优化：

#include<bits/stdc++.h>
#define ll long long
using namespace std;

template <class T>void read(T &x){
	x=0;
	char c,d='0';
	c=getchar();
	while(c<'0'||c>'9'){
		d=c;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=(x<<3)+(x<<1)+c-'0';
		c=getchar();
	}
	if(d=='-') x=-x;
}
template <class T>void wt(T x){
	if(x/10) wt(x/10);
	putchar(x%10+'0');
}
template <class T>void write_enter(T x){
	if(x<0){
		x=-x;
		putchar('-');
	}
	wt(x);
	putchar('\n');
}
template <class T>void write_space(T x){
	if(x<0){
		x=-x;
		putchar('-');
	}
	wt(x);
	putchar(' ');
}

const int N=205,maxn=0x3f3f3f3f;
int n,head[N*N],cur[N*N],tot=2,s,t;
struct edge{
	int to,nex,cap;
}e[(N*N<<3)+(N*N<<1)];
inline void add(int u,int v,int cap){
	e[tot].nex=head[u];
	head[u]=tot;
	e[tot].to=v;
	e[tot++].cap=cap;
}
inline void addedge(int u,int v,int cap){
	add(u,v,cap);
	add(v,u,0);
}
int dep[N*N];
inline bool bfs(){
	memset(dep,0,sizeof(dep));
	memcpy(cur,head,sizeof(head));
	queue <int> q;
	q.push(s);
	dep[s]=1;
	while(!q.empty()){
		int u=q.front();
		q.pop();
		for(int k=head[u];k;k=e[k].nex){
			int v=e[k].to,cap=e[k].cap;
			if(dep[v]||!cap) continue;
			dep[v]=dep[u]+1;
			q.push(v);
		}
	}
	return dep[t]? 1:0;
}
bool vis[N*N];
inline ll dfs(int u,int f){
	if(u==t||!f) return f;
	int maxf=0,tf;
	vis[u]=1;
	for(int &k=cur[u];k&&f;k=e[k].nex){
		int v=e[k].to,cap=e[k].cap;
		if(dep[v]!=dep[u]+1||!cap) continue;
		tf=dfs(v,min(f,cap));
		f-=tf,maxf+=tf;
		e[k].cap-=tf,e[k^1].cap+=tf;
	}
	return maxf;
}
inline int dinic(){
	int res=0,x;
	while(bfs())
		while((x=dfs(s,maxn))) res+=x;
	return res;
}
#define P(i,j) ((i-1)*n+j)
#define chk(i) (1<=i&&i<=n)
int plux[8]={1,1,2,2,-1,-1,-2,-2},pluy[8]={2,-2,1,-1,2,-2,1,-1};
int numb;
map <tuple<int,int>,bool> mp;
int main(){
	read(n),read(numb);
	for(int i=1;i<=numb;i++){
		int x,y;
		read(x),read(y);
		mp[tie(x,y)]=1;
	}
	s=n*n+1,t=n*n+2;
	int sum=0,pj;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)if(!mp[tie(i,j)]){
			pj=1,sum+=pj;
			if((i+j)%2==0){
				addedge(s,P(i,j),pj);
				for(int opt=0;opt<8;opt++){
					int x=i+plux[opt],y=j+pluy[opt];
					if(chk(x)&&chk(y)&&!mp[tie(x,y)]) addedge(P(i,j),P(x,y),maxn);
				}
			}
			else addedge(P(i,j),t,pj);
		}
	write_enter(sum-dinic());
	return 0;
}