#include <iostream>
#include <math.h>
#include <vector>
#include <algorithm>

int main() {
    double x1, y1, x2, y2, x3, y3;
    std::cin>>x1>>y1>>x2>>y2>>x3>>y3;

    double maxD, AB, AC, BC;
    AB = sqrt((x1 - x2)*(x1 - x2) + (y1 - y2)*(y1 - y2));
    AC = sqrt((x3 - x1)*(x3 - x1) + (y3 - y1)*(y3 - y1));
    BC = sqrt((x3 - x2)*(x3 - x2) + (y3 - y2)*(y3 - y2));
    maxD = std::max(AB, std::max(AC, BC));
    double R = maxD / 2, xC, yC, L;

    if(maxD == AB) {
        xC = (x1 + x2) / 2; yC = (y1 + y2) / 2;
        L = sqrt((x3 - xC)*(x3 - xC) + (y3 - yC)*(y3 - yC));
    }
    else if(maxD == AC) {
        xC = (x1 + x3) / 2; yC = (y1 + y3) / 2;
        L = sqrt((x2 - xC)*(x2 - xC) + (y2 - yC)*(y2 - yC));
    }
    else {
        xC = (x2 + x3) / 2; yC = (y2 + y3) / 2;
        L = sqrt((x1 - xC)*(x1 - xC) + (y1 - yC)*(y1 - yC));
    }

    printf("%.7f\n",abs(L-R));
}