#include <iostream>
#include <cstdio>
#include <iomanip>


using namespace std;
double xg, yg;
double r;

double stred(double x1, double y1, double x2, double y2, double x3, double y3) {
	int x = x1 + x2, y = y1 + y2;
	xg = x / 2.0;
	yg = y / 2.0;
	r = sqrt(pow(xg - x1, 2) + pow(yg - y1, 2));

	//cout << "r " << r << "\n";
	//cout << "xg " << xg << " yg " << yg << "\n";
	double res = sqrt(pow(xg - x3, 2) + pow(yg - y3, 2)) - r;
	//cout << "res " << res << "\n";
	return res;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	
	double x1, y1, x2, y2, x3, y3;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

	double o1 = stred(x1, y1, x2, y2, x3, y3);

	o1 = min(o1, stred(x2, y2, x3, y3, x1, y1));
	o1 = min(o1, stred(x3, y3, x1, y1, x2, y2));

	cout << setprecision(7) << abs(o1);
	return 0;
}