40分求助

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,m,k,x,y;
	cin>>n>>m>>k;
	int a[n][n];
	memset(a,0,sizeof(a));
	for(int i=2;i<=m+1;i++)
	{
		cin>>x>>y;
		a[x][y]=1;
		a[x-1][y]=1;
		a[x-2][y]=1;
		a[x][y-1]=1;
		a[x][y-2]=1;
		a[x][y+1]=1;
		a[x][y+2]=1;
		a[x-1][y]=1;
		a[x-2][y]=1;
		a[x-1][y-1]=1;
		a[x+1][y-1]=1;
		a[x-1][y+1]=1;
		a[x+1][y+1]=1;
	}
	if(k>0)
	{
		for(int i=m+2;i<m+k+1;i++)
		{
			cin>>x>>y;
			a[x][y]=1;
			a[x-1][y]=1;
			a[x-2][y]=1;
			a[x][y-1]=1;
			a[x][y-2]=1;
			a[x][y+1]=1;
			a[x][y+2]=1;
			a[x-1][y]=1;
			a[x-2][y]=1;
			
			a[x+1][y-1]=1;
			a[x+2][y-1]=1;
			a[x+1][y-2]=1;
			a[x+2][y-2]=1;
			
			a[x+1][y+1]=1;
			a[x+2][y+1]=1;
			a[x+1][y+2]=1;
			a[x+2][y+2]=1;
			
			a[x-1][y-1]=1;
			a[x-2][y-1]=1;
			a[x-1][y-2]=1;
			a[x-2][y-2]=1;
			
			a[x-1][y+1]=1;
			a[x-2][y+1]=1;
			a[x-1][y+2]=1;
			a[x-2][y+2]=1;
		}
	}
	int zzg=0;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(a[i][j]==0)
				zzg+=1;
		}
	}
	cout<<zzg;
}