Problem: A maze is composed of a grid of H \times W squares - H vertical, W horizontal.

The square at the i-th row from the top and the j-th column from the left - (i,j) - is a wall if S_{ij} is `#` and a road if S_{ij} is `.`.

There is a magician in (C_h,C_w). He can do the following two kinds of moves:

* Move A: Walk to a road square that is vertically or horizontally adjacent to the square he is currently in.
* Move B: Use magic to warp himself to a road square in the 5\times 5 area centered at the square he is currently in.



In either case, he cannot go out of the maze.

At least how many times does he need to use the magic to reach (D_h, D_w)?

Constraints

* 1 \leq H,W \leq 10^3
* 1 \leq C_h,D_h \leq H
* 1 \leq C_w,D_w \leq W
* S_{ij} is `#` or `.`.
* S_{C_h C_w} and S_{D_h D_w} are `.`.
* (C_h,C_w) \neq (D_h,D_w)

Input

Input is given from Standard Input in the following format:


H W
C_h C_w
D_h D_w
S_{11}\ldots S_{1W}
\vdots
S_{H1}\ldots S_{HW}


Output

Print the minimum number of times the magician needs to use the magic. If he cannot reach (D_h,D_w), print `-1` instead.

Examples

Input

4 4
1 1
4 4
..#.
..#.
.#..
.#..


Output

1


Input

4 4
1 4
4 1
.##.


.##.


Output

-1


Input

4 4
2 2
3 3
....
....
....
....


Output

0


Input

4 5
1 2
2 5
.###
.
..##
..##


Output

2

Solution (in CPP):

Solution:
#include <cstdio>
#include <deque>
struct dot{
    int x,y,step;
};
std::deque<dot> q;//开双端队列
int h,w,ch,cw,dh,dw;
char s[1003][1003];
bool vis[1003][1003];
const int dx[]={-1,0,1,0},dy[]={0,1,0,-1};//方向数组
int main(){
    scanf("%d%d%d%d%d%d",&h,&w,&ch,&cw,&dh,&dw);
    for(int i=1;i<=h;i++) scanf("%s",s[i]+1);
    //采取上面的方式读入可以防止不必要的字符被读入
    q.push_back((dot){ch,cw,0});//第一次前面后面入队都行
    while(!q.empty()){
        dot t=q.front();q.pop_front();
        if(t.x==dh&&t.y==dw){
            printf("%d\n",t.step);
            return 0;
        }
        vis[t.x][t.y]=1;
        //使用A方式移动：
        for(int i=0;i<4;i++){
            int tx=t.x+dx[i],ty=t.y+dy[i];
            if(tx>=1&&tx<=h&&ty>=1&&ty<=w&&!vis[tx][ty]&&s[tx][ty]=='.')
                q.push_front((dot){tx,ty,t.step});//插入队列前面
        }
        //使用魔法移动：
        for(int tx=t.x-2;tx<=t.x+2;tx++)
            for(int ty=t.y-2;ty<=t.y+2;ty++)
                if(tx>=1&&tx<=h&&ty>=1&&ty<=w&&!vis[tx][ty]&&s[tx][ty]=='.'){
                    if(t.x==tx&&t.y==ty) continue;
                    q.push_back((dot){tx,ty,t.step+1});//插入队列后面
                }
    }
    puts("-1");
    return 0;
}