求助大佬T^T

#include<iostream>
using namespace std;
int a[105][105]={0};
int main(){
    int n,s=0;
    cin>>n;
    int m,k;
    cin>>m>>k;
    int x,y;
    for(int i=1;i<=m;i++){
        cin>>x>>y;
        a[x][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-1][y-1]=1;
        a[x-1][y]=1;
        a[x-1][y+1]=1;
        a[x+1][y-1]=1;
        a[x+1][y+1]=1;
        a[x-2][y]=1;
        a[x+2][y]=1;
    }
    for(int i=1;i<=k;i++){
        cin>>x>>y;
        a[x][y]=1;
        a[x-2][y-2]=1;
        a[x-1][y-2]=1;
        a[x][y-2]=1;
        a[x+1][y-2]=1;
        a[x+2][y-2]=1;
        a[x-2][y-1]=1;
        a[x-1][y-1]=1;
        a[x][y-1]=1;
        a[x+1][y-1]=1;
        a[x+2][y-1]=1;
        a[x-2][y]=1;
        a[x-1][y]=1;
        a[x][y]=1;
        a[x+1][y]=1;
        a[x+2][y]=1;
        a[x-2][y+1]=1;
        a[x-1][y+1]=1;
        a[x][y+1]=1;
        a[x+1][y+1]=1;
        a[x+2][y+1]=1;
        a[x-2][y+2]=1;
        a[x-1][y+2]=1;
        a[x][y+2]=1;
        a[x+1][y+2]=1;
        a[x+2][y+2]=1;
    }
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            if(a[i][j]==0){
                s++;
            }
        }
    }
    cout<<s;
    return 0;
}