#include <iostream>
#include <bits/stdc++.h>

#define ll long long
using namespace std;

struct Vec {
    long double x, y;

    void load(){
        cin >> x;
        cin >> y;
    }
    Vec operator+(Vec rhs){
        return Vec{x + rhs.x, y + rhs.y};
    }
    Vec operator-(Vec rhs){
        return Vec{x - rhs.x, y - rhs.y};
    }
    Vec operator*(long double rhs){
        return Vec{x *rhs, y *rhs};
    }
    long double len(){
        return sqrt(x * x + y*y);
    }
    void print(){
        cout << x << " " << y << endl;
    }
};

long double distpow2_from(Vec &a, Vec &b, Vec &point){
    auto center = (b - a)*0.5 + a;
    auto out = center - point;
    return abs(out.len()  -  ((b - a)*0.5).len());
}

void solve(){
    Vec a, b, c;
    a.load();
    b.load();
    c.load();
    long double out = distpow2_from(a,b,c);
    long double out2 = distpow2_from(c,a,b);
    long double out3 = distpow2_from(b,c,a);

    if(out > out2){
        out = out2;
    }
    if(out > out3){
        out = out3;
    }
    cout << out << endl;
}


int main() {
    solve();
    return 0;
}