C++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 qw=0;
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=n;j++)
        {
            if(a[i][j]==0)
                qw+=1;
        }
    }
    cout<<qw;
}