为啥是60分呢(⊙_⊙)?

各位大佬帮忙看看，为啥子是60分呢？？？ #include<bits/stdc++.h> using namespace std; const int N=10000; bool a[N][N]; int n,m,k,i,j; int x,y,s=0; int main(){ cin>>n>>m>>k; for(i=1;i<=m;i++){ cin>>x>>y; a[x][y]=1; a[x-1][y]=1; a[x-2][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]=1; a[x-1][y+1]=1; a[x+1][y-1]=1; a[x+1][y+1]=1; } for(i=1;i<=k;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-2][y]=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-2]=1; a[x-1][y+2]=1; a[x+1][y-1]=1; a[x+1][y+1]=1; a[x+1][y+2]=1; a[x+1][y-2]=1; a[x-2][y-2]=1; a[x-2][y-1]=1; a[x-2][y+1]=1; a[x-2][y+2]=1; a[x+2][y+2]=1; a[x+2][y+1]=1; a[x+2][y-1]=1; a[x+2][y-2]=1; } for(i=1;i<=n;i++) for(j=1;j<=n;j++) if(a[i][j]==0)s++; cout<<s; return 0; } 好伤心呜呜呜