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];
	dp1[y][x]=-1;
	if(d==1){
	}else if(dp1[y-1][x]==d-1){
		f2(y-1,x);
	}else if(dp1[y+1][x]==d-1){
		f2(y+1,x);
	}else if(dp1[y][x-1]==d-1){
		f2(y,x-1);
	}else if(dp1[y][x+1]==d-1){
		f2(y,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 f4(int r,int c,int vy,int vx){
	for(int y=0;y<h;++y){
		for(int x=0;x<w;++x){
			dp1[y][x]=0;
		}
	}
	qr=qw=0;
	{
		int y=r+vy;
		int x=c+vx;
		if(s[y][x]=='.'){
			dp1[y][x]=1;
			if(s[y+vy][x+vx]=='.'){
				enq(y+vy,x+vx,0,2);
			}
			if(s[y-vx][x+vy]=='.'){
				enq(y-vx,x+vy,0,2);
			}
			if(s[y+vx][x-vy]=='.'){
				enq(y+vx,x-vy,0,2);
			}
		}
	}
	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);
		}
	}
	return dp1[r][c];
}

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,-1,0);if(d>0&&d2>d+d1+2)d2=d+d1+2;
		d=f4(ra,ca,+1,0);if(d>0&&d2>d+d1+2)d2=d+d1+2;
		d=f4(ra,ca,0,-1);if(d>0&&d2>d+d1+2)d2=d+d1+2;
		d=f4(ra,ca,0,+1);if(d>0&&d2>d+d1+2)d2=d+d1+2;
		d=f4(rb,cb,-1,0);if(d>0&&d2>d+d1+2)d2=d+d1+2;
		d=f4(rb,cb,+1,0);if(d>0&&d2>d+d1+2)d2=d+d1+2;
		d=f4(rb,cb,0,-1);if(d>0&&d2>d+d1+2)d2=d+d1+2;
		d=f4(rb,cb,0,+1);if(d>0&&d2>d+d1+2)d2=d+d1+2;
	}
	if(d2==3000000){
		puts("-1");
		exit(0);
	}
	printf("%d",d1+d2);
}