int h,w,ra,ca,rb,cb;
char s[1333][1335];

int dp1[1333][1333];
int dp2[1333][1333][2];

struct{int y,x,z,d} q[16000000];
int qr,qw;

void enq(int y,int x,int z,int d){
	q[qw].y=y;
	q[qw].x=x;
	q[qw].z=z;
	q[qw].d=d;
	++qw;
}

void f1(){
	qr=qw=0;
	enq(ra,ca,0,1);
	while(qr<qw){
		int y=q[qr].y;
		int x=q[qr].x;
		int d=q[qr].d;
		++qr;
		if(s[y][x]=='.'&&dp1[y][x]==0){
			dp1[y][x]=d;
			enq(y-1,x,0,d+1);
			enq(y+1,x,0,d+1);
			enq(y,x-1,0,d+1);
			enq(y,x+1,0,d+1);
		}
	}
}

void f2(int y,int x){
	int d=dp1[y][x];
	while(1){
		dp1[y][x]=-1;
		--d;
		if(d==0){
			return;
		}else if(dp1[y-1][x]==d){
			y=y-1;
		}else if(dp1[y+1][x]==d){
			y=y+1;
		}else if(dp1[y][x-1]==d){
			x=x-1;
		}else if(dp1[y][x+1]==d){
			x=x+1;
		}
	}
}

void f3(){
	qr=qw=0;
	enq(ra,ca,0,1);
	while(qr<qw){
		int y=q[qr].y;
		int x=q[qr].x;
		int z=q[qr].z;
		int d=q[qr].d;
		++qr;
		if(s[y][x]=='.'&&dp2[y][x][z]==0&&(z?!(y==ra&&x==ca):!(y==rb&&x==cb))){
			dp2[y][x][z]=d;
			if(z==0&&dp1[y][x]>=0){
				enq(y,x,1,d+1);
			}
			enq(y-1,x,z,d+1);
			enq(y+1,x,z,d+1);
			enq(y,x-1,z,d+1);
			enq(y,x+1,z,d+1);
		}
	}
}

int f4a(int r,int c){
	return s[r][c]=='.'&&dp1[r][c]>=0;
}
int f4(int r,int c){
	int d=1;
	while(1){
		dp1[r][c]=-1;
		int a=f4a(r-1,c)+f4a(r+1,c)+f4a(r,c-1)+f4a(r,c+1);
		if(a>=2){
			return d*4;
		}
		if(a==0){
			return 3000000;
		}
		r+=f4a(r+1,c)-f4a(r-1,c);
		c+=f4a(r,c+1)-f4a(r,c-1);
		d+=1;
	}
}

main(){
	scanf("%d%d%d%d%d%d",&h,&w,&ra,&ca,&rb,&cb);
	--ra;--ca;--rb;--cb;
	for(int y=0;y<h;++y){
		scanf("%s",s[y]);
	}
	f1();
	int d1=dp1[rb][cb]-1;
	if(d1<0){
		puts("-1");
		exit(0);
	}
	f2(rb,cb);
	f3();
	int d2=dp2[rb][cb][1]-2;
	if(d2<0){
		d2=3000000;
	}
	int d;
	d=f4(ra,ca)+d1;
	if(d2>d) d2=d;
	d=f4(rb,cb)+d1;
	if(d2>d) d2=d;
	if(d2==3000000){
		puts("-1");
		exit(0);
	}
	printf("%d",d1+d2);
}