#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
const double N=1e-9;
double kx,ky,kex,key,ox,oy,oex,oey;
double add;
bool flag=false;
double dx,dy;
double dis(double x,double y,double xi,double yi){
	return sqrt((x-xi)*(x-xi)+(y-yi)*(y-yi));
}

bool isvaild(double x,double y){
	bool xi=(x>=min(ox,oex)&&x<=max(ox,oex));
	bool yi=(y>=min(oy,oey)&&y<=max(oy,oey));
	return xi&&yi;
}

double f(double x,double y){
	double cur=dis(x,y,kx,ky);
	double nextx,nexty;
	if(flag){
		nextx=ox,nexty=oy+(dy*cur);
	} 
	else{
		double addx=sqrt((cur*cur)/(add*add+1));
		double addy=add*addx;
		nextx=ox+dx*addx,nexty=oy+dy*addy;
		
	}
	if(!isvaild(nextx,nexty)){
		nextx=oex,nexty=oey;
	}
	//cout<<"\xb2\xe2\xca\xd4"<<x<<" "<<y<<" "<<nextx<<" "<<nexty<<" "<<endl;
	return dis(x,y,nextx,nexty);
}

int main(){
	cin>>kx>>ky>>ox>>oy>>kex>>key>>oex>>oey;
	double d1=dis(kx,ky,ox,oy);
	double d2=dis(kex,key,oex,oey);
	
	if(oex==ox) flag=true;
	else add=(oey-oy)/(oex-ox);
	//cout<<add<<endl;
	dy=(oey>oy?1:-1);
	dx=(oex>ox?1:-1);
	
	
	double lx=kx,ly=ky,rx=kex,ry=key;
	while(dis(lx,ly,rx,ry)>N){
		//cout<<"\xcf\xd6\xd4\xda:"<<lx<<" "<<ly<<" "<<rx<<" "<<ry<<" "<<f(lx,ly)<<" "<<N<<endl;
		//cout<<endl;
		double xtemp=(rx-lx)/3;
		double ytemp=(ry-ly)/3;
		double Lx=lx+xtemp,Rx=rx-xtemp;
		double Ly=ly+ytemp,Ry=ry-ytemp;
		if(f(Lx,Ly)>f(Rx,Ry)) rx=Rx,ry=Ry;
		else lx=Lx,ly=Ly;
	}
	
	double res=max(f(lx,ly),max(d1,d2));
	if(res) cout<<fixed<<setprecision(10)<<res;
	else cout<<res;
	return 0;
}