#include <stdio.h>
#include <math.h>

double dist(double ax, double ay, double bx, double by, double cx, double cy){
    double hx = (ax + bx) / 2;
    double hy = (ay + by) / 2;
    double r = sqrt((ax - bx) * (ax - bx) + (ay - by) * (ay - by)) / 2;
    double l = sqrt((hx - cx) * (hx - cx) + (hy - cy) * (hy - cy));
    return l - r;
}

int main(){
    double ax, ay, bx, by, cx, cy;
    scanf("%lf %lf %lf %lf %lf %lf", &ax, &ay, &bx, &by, &cx, &cy);
    double a = fabs(dist(bx, by, cx, cy, ax, ay));
    double b = fabs(dist(ax, ay, cx, cy, bx, by));
    double c = fabs(dist(bx, by, ax, ay, cx, cy));
    double min = a < b ? a : b;
    min = min < c ? min : c;
    printf("%lf\n", min);
    return 0;
}