#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
char*rp;
#define RD(v) v=0;{int _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}

int h,w,ra,ca,rb,cb;
static inline
int s(int y,int x){
	return rp[y*w+x];
}

#define INF 30000000

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

struct{int y,x,z,d;} q[1<<16];
int qr,qw;

static inline
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=(qw+1)&(1<<16)-1;
}

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=(qr+1)&(1<<16)-1;
		if(s(y,x)=='.'&&dp1[y][x]==0){
			dp1[y][x]=d;
			++d;
			enq(y-1,x,0,d);
			enq(y+1,x,0,d);
			enq(y,x-1,0,d);
			enq(y,x+1,0,d);
		}
	}
}

void f2(int y,int x){
	int d=dp1[y][x];
	while(dp1[y][x]=-1,--d){
		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=(qr+1)&(1<<16)-1;
		if(s(y,x)=='.'&&dp2[y][x][z]==0&&(z?!(y==ra&&x==ca):!(y==rb&&x==cb))){
			dp2[y][x][z]=d;
			if(y==rb&&x==cb){
				return;
			}
			if(z==0&&dp1[y][x]>=0){
				enq(y,x,1,d);
			}
			++d;
			enq(y-1,x,z,d);
			enq(y+1,x,z,d);
			enq(y,x-1,z,d);
			enq(y,x+1,z,d);
		}
	}
}

static inline
int f4a(int y,int x,int py,int px){
	return !(y==py&&x==px)&&s(y,x)=='.'&&dp1[y][x]>=0;
}
int f4(int y,int x){
	int py=-1,px=-1;
	int d=1;
	while(1){
		int a1=f4a(y-1,x,py,px);
		int a2=f4a(y+1,x,py,px);
		int a3=f4a(y,x-1,py,px);
		int a4=f4a(y,x+1,py,px);
		int a=a1+a2+a3+a4;
		if(a>=2){
			return d*4;
		}
		if(a==0){
			return INF;
		}
		py=y;
		px=x;
		y+=a2-a1;
		x+=a4-a3;
		d+=1;
	}
}

main(){
	rp=mmap(0l,1l<<28,1,2,0,0ll);
	RD(h);
	RD(w);++w;
	RD(ra);--ra;
	RD(ca);--ca;
	RD(rb);--rb;
	RD(cb);--cb;
	f1();
	int d1=dp1[rb][cb]-1;
	if(d1<0){
		goto end;
	}
	f2(rb,cb);
	f3();
	int d2=dp2[rb][cb][1]-1;
	if(d2<0){
		d2=INF;
	}
	int d;
	d=f4(ra,ca)+d1;
	if(d2>d) d2=d;
	d=f4(rb,cb)+d1;
	if(d2>d) d2=d;
	if(d2==INF){
		d1=-1;
		goto end;
	}
	d1+=d2;
	end:;
	printf("%d",d1);
}