#include <bits/stdc++.h>

using namespace std;
#define ld long double
#define ll long long


ld distPoints(ld x1, ld y1, ld x2, ld y2) {
    return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

ld calc(ld xm, ld ym, ld rad, ld xNeed, ld yNeed, ld a) {
    ld x = xm + rad * cos(a);
    ld y = ym + rad * sin(a);
    return distPoints(x, y, xNeed, yNeed);
}

ld solveCircle(ld xm, ld ym, ld rad, ld xNeed, ld yNeed, ld a1, ld a2) {
    ld l = a1, r = a2;
    while (r - l >= 0.000000001) {
        ld m1 = l + (r - l)/3.0;
        ld m2 = r - (r - l)/3.0;

        ld f1 = calc(xm, ym, rad, xNeed, yNeed, m1);
        ld f2 = calc(xm, ym, rad, xNeed, yNeed, m2);
        
        if (f1 < f2) r = m2;
        else if (f1 > f2) l = m1;
        else {
            l = m1;
        }
    }
    return calc(xm, ym, rad, xNeed, yNeed, l);
}

ld solveMid(int x1, int y1, int x2, int y2, int x3, int y3) {
    ld xm = (ld)(x1 + x2) / 2.0;
    ld ym = (ld)(y1 + y2) / 2.0;

    ld r = distPoints(xm, ym, x1, y1);

    return min({solveCircle(xm, ym, r, x3, y3, 0.0, 90.0), 
                solveCircle(xm, ym, r, x3, y3, 90.0, 180.0), 
                solveCircle(xm, ym, r, x3, y3, 180.0, 270.0), 
                solveCircle(xm, ym, r, x3, y3, 270.0, 360.0)
    });
}

pair<int, int> t[5];

int main() {
    for (int i = 1; i <= 3; i++) {
        cin >> t[i].first >> t[i].second;
    }

    ld ans = 1010101010;

    for (int i = 1; i <= 3; i++) {
        for (int j = i + 1; j <= 3; j++) {
            if (i == j) continue;
            int k = 1;
            while (k == i || k == j) k++;

            ans = min(ans, solveMid(t[i].first, t[i].second, t[j].first, t[j].second, t[k].first, t[k].second));
        }
    }
    
    cout << fixed << setprecision(9) << ans << '\n';
    return 0;
}

/*
4 0
0 4
-1 -1
*/