80分，求助第1个点过不去

#include<stdio.h>
int main() {
	int i,j,c,b,q=0,n,m,k,x,y;
	int a[1000][1000]= {0};
	scanf("%d%d%d\n",&n,&m,&k);
	for(i=2; i<=m+1; i++) {
		scanf("%d%d\n",&x,&y);
		a[x+2][y]=1;
		a[x+1][y]=1;
		a[x-2][y]=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-1][y+1]=1;
		a[x][y-2]=1;
		a[x][y-1]=1;
		a[x][y+1]=1;
		a[x][y+2]=1;
	}
	for(j=m+2; j<=m+k+1; j++) {
		scanf("%d%d\n",&x,&y);
		for(c=x-2; c<=x+2; c++) {
			for(b=y-2; b<=y+2; b++) {
				a[c][b]=1;
			}
		}
	}
	for(x=1; x<=n; x++) {
		for(y=1; y<=n; y++) {
			if(a[x][y]==0)
				q++;
		}

	}
	printf("%d",q);
	return 0;
}