#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

template <typename T>
ostream& operator<< (ostream& os, const vector<T> & v) {
    os << "[ ";
    for (const T & elem : v) {
        os < elem << " ";
    }
    os << " ]";
    return os;
}

double distance(double x1, double y1, double x2, double y2) {
    double dx = x1 - x2;
    double dy = y1 - y2;
    return sqrt(dx * dx + dy * dy);
}

double move_first(double x1, double y1, double x2, double y2, double x3, double y3) {
    double center_x = (x2 + x3) / 2;
    double center_y = (y2 + y3) / 2;

    double radius = distance(x2, y2, x3, y3) / 2;
    double p1_to_center_dist = distance(x1, y1, center_x, center_y);

    return abs(p1_to_center_dist - radius);    
}

void test_case() {
    ll x1, y1, x2, y2, x3, y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

    double result = min(move_first(x1, y1, x2, y2, x3, y3), min(move_first(x2, y2, x1, y1, x3, y3), move_first(x3, y3, x1, y1, x2, y2)));
    cout << result << endl;
}

int main() {
    cin.tie(0);
    cout.tie(0);
    cin.exceptions(ios::failbit);
    ios::sync_with_stdio(false);
    ll t = 1;
    // cin >> t; // potential comment
    while (t--) {
        test_case();
    }
    return 0;
}