这是一年前写的程序，20分，看不出来哪有问题。

#include<iostream>
#include<cstring>
using namespace std;
int a[110][110],x,y,n;
void ys(){
    int x1 = x-2,x2 = x+2,y1 = y-2,y2 = y+2;
    for(int i = x1;i<=x2;i++){
        for(int j = y1;j<=y2;j++){
			a[i][j] = 1;
        }
    }
}
void hb(){
	a[x][y] = 1;
    if(x-2>=0)a[x-2][y] = 1;
    if(x+2<=n)a[x+2][y] = 1;
    if(y-2>=0)a[x][y-2] = 1;
    if(y+2<=n)a[x][y+2] = 1;
    if(x-1>=0)a[x-1][y] = 1;
    if(x+1<=n)a[x+1][y] = 1;
    if(y-1>=0)a[x][y-1] = 1;
    if(y+1<=n)a[x][y+1] = 1;
}
int main() {
    int m,k;
    cin>>n>>m>>k;
    for(int o = 1;o<=m;o++){
        cin>>x>>y;
        hb();
    }
    for(int o = 1;o<=k;o++){
        cin>>x>>y;
        ys();
    }
    int cnt = 0;
    for(int i = 1;i<=n;i++){
        for(int j = 1;j<=n;j++){
            if(a[i][j]==0)cnt++;
        }
    }
    cout<<cnt;
    return 0;
}