20分求助！

#include <iostream>
using namespace std;
struct xy
{
    int x,y;
};
bool m[110][110];
int n,m1,k,ans;
xy hb[10010],ys[10010];
int main()
{
    cin>>n>>m1>>k;
    for (int i=1;i<=m1;i++)
    {
        cin>>hb[i].x>>hb[i].y;
        int x=hb[i].x,y=hb[i].y;
        m[x][y]=1;
        m[x+1][y]=1;
        m[x+2][y]=1;
        m[x-1][y]=1;
        m[x-2][y]=1;
        m[x][y+1]=1;
        m[x][y+2]=1;
        m[x][y-1]=1;
        m[x][y-2]=1;
    }
    for (int i=1;i<=k;i++)
    {
        cin>>ys[i].x>>ys[i].y;
        int x=ys[i].x,y=ys[i].y;
        m[x][y]=1;
        m[x+1][y]=1;
        m[x+2][y]=1;
        m[x-1][y]=1;
        m[x-2][y]=1;
        m[x][y+1]=1;
        m[x][y+2]=1;
        m[x][y-1]=1;
        m[x][y-2]=1;
        m[x+2][y+2]=1;
        m[x+1][y+2]=1;
        m[x+2][y+1]=1;
        m[x+1][y+1]=1;
        m[x-2][y+2]=1;
        m[x-1][y+2]=1;
        m[x-2][y+1]=1;
        m[x-1][y+1]=1;
        m[x+2][y-2]=1;
        m[x+1][y-2]=1;
        m[x+2][y-1]=1;
        m[x+1][y-1]=1;
        m[x-2][y-2]=1;
        m[x-1][y-2]=1;
        m[x-2][y-1]=1;
        m[x-1][y-1]=1;
    }
    for (int i=1;i<=n;i++)
        for (int j=1;j<=n;j++)
            if (!m[i][j])
                ans++;
    cout<<ans;
    return 0;
}