#include <bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define len(x) (int)(x.size())
#define all(vs) vs.begin(), vs.end()
using ll = long long;
using ii = pair<int, int>;
using iii = pair<int, ii>;
#define MAXN 1010

char mt[MAXN][MAXN];
int  mem[MAXN][MAXN];
int n, m;

inline bool is_valid(int i, int j, int w){
	return  ((i>=0 and i<n) and (j>=0 and j<m) and (mt[i][j]=='.') and (mem[i][j]==-1 or w<mem[i][j]));
}
int32_t main(){
	ios::sync_with_stdio(0);
	memset(mem, -1, sizeof mem);
	cin >> n >> m;
	int cx, dx, cy, dy;
	cin >> cx >> cy >> dx >> dy;
	--cx; --cy; --dx; --dy;
	for(int i=0; i<n; ++i)
		cin >> mt[i];
	priority_queue<iii> q;
	q.push({0, {cx, cy}});
	while(not q.empty()){
		int w = -q.top().ff;
		int x = q.top().ss.ff;
		int y = q.top().ss.ss; q.pop();
		if(mem[x][y]!=-1 and mem[x][y]<=w) continue;
		mem[x][y] = w;
		if(is_valid(x-1, y, w))
			q.push({-w, {x-1, y}});
		if(is_valid(x+1, y, w))
			q.push({-w, {x+1, y}});
		if(is_valid(x, y-1, w))
			q.push({-w, {x, y-1}});
		if(is_valid(x, y+1, w))
			q.push({-w, {x, y+1}});
		for(int i=x-2; i<=x+2; ++i){
			for(int j=y-2; j<=y+2; ++j){
				if(is_valid(i, j, w+1)){
					q.push({-(w+1), {i, j}});
				}
			}
		}
	}
	cout << mem[dx][dy] << endl;
}

### Prompt

Develop a solution in cpp to the problem described below:

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

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define len(x) (int)(x.size())
#define all(vs) vs.begin(), vs.end()
using ll = long long;
using ii = pair<int, int>;
using iii = pair<int, ii>;
#define MAXN 1010

char mt[MAXN][MAXN];
int  mem[MAXN][MAXN];
int n, m;

inline bool is_valid(int i, int j, int w){
	return  ((i>=0 and i<n) and (j>=0 and j<m) and (mt[i][j]=='.') and (mem[i][j]==-1 or w<mem[i][j]));
}
int32_t main(){
	ios::sync_with_stdio(0);
	memset(mem, -1, sizeof mem);
	cin >> n >> m;
	int cx, dx, cy, dy;
	cin >> cx >> cy >> dx >> dy;
	--cx; --cy; --dx; --dy;
	for(int i=0; i<n; ++i)
		cin >> mt[i];
	priority_queue<iii> q;
	q.push({0, {cx, cy}});
	while(not q.empty()){
		int w = -q.top().ff;
		int x = q.top().ss.ff;
		int y = q.top().ss.ss; q.pop();
		if(mem[x][y]!=-1 and mem[x][y]<=w) continue;
		mem[x][y] = w;
		if(is_valid(x-1, y, w))
			q.push({-w, {x-1, y}});
		if(is_valid(x+1, y, w))
			q.push({-w, {x+1, y}});
		if(is_valid(x, y-1, w))
			q.push({-w, {x, y-1}});
		if(is_valid(x, y+1, w))
			q.push({-w, {x, y+1}});
		for(int i=x-2; i<=x+2; ++i){
			for(int j=y-2; j<=y+2; ++j){
				if(is_valid(i, j, w+1)){
					q.push({-(w+1), {i, j}});
				}
			}
		}
	}
	cout << mem[dx][dy] << endl;
}

```