求修改代码，开o2就RE

#include<bits/stdc++.h>
#include<vector>
using namespace std;
long long x1,x2,y11,y2,book[2000][2000],tail=1,hand=1,ty,tx,flag,book1[2000][2000];
struct sb
{
	int x;
	int y;
	int s;
}a[1000000],b[1000000];
int main()
{
	int qwe[12][2]={{-2,2},{-2,1},{-1,2},{2,2},{2,1},{1,2},{-2,-2},{-2,-1},{-1,-2},{2,-1},{1,-2}/*,{2,-2}*/}; 
	cin>>x1>>y11>>x2>>y2;
	book[x1][y11]=1;
	a[hand].x=x1;
	a[hand].y=y11;
	tail++;
	while(hand<tail)
	{
		for(int i=0;i<13;i++)
		{
			tx=a[hand].x+qwe[i][0];
			ty=a[hand].y+qwe[i][1];
			if(tx<1 or ty<1) continue;
			if(book[tx][ty]==0)
			{
				book[tx][ty]=1;
				a[tail].x=tx;
				a[tail].s=a[hand].s+1; 
				a[tail].y=ty;
				tail++;
			}
			if(a[tail-1].x==1 and a[tail-1].y==1)
			{
				flag=1;
				break;
			 } 
			 
		}
		if(flag==1) break;
		hand++;
	}
	cout<<a[tail-1].s<<endl;
	
	
	
	
	flag=0;
	hand=1;
	tail=1;
	book[x2][y2]=1;
	b[hand].x=x2;
	b[hand].y=y2;
	tail++;
	while(hand<tail)
	{
		for(int i=0;i<13;i++)
		{
			tx=b[hand].x+qwe[i][0];
			ty=b[hand].y+qwe[i][1];
			if(tx<1 or ty<1) continue;
			if(book1[tx][ty]==0)
			{
				book1[tx][ty]=1;
				b[tail].x=tx;
				b[tail].s=b[hand].s+1; 
				b[tail].y=ty;
				tail++;
			}
			if(b[tail-1].x==1 and b[tail-1].y==1)
			{
				flag=1;
				break;
			 } 
			 
		}
		if(flag==1) break;
		hand++;
	}
	cout<<b[tail-1].s;
	return 0;
}