390.cpp

#include <stdio.h>
#include <algorithm>

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

double min_distance(double x1, double y1, double x2, double y2, double xc, double yc) {
    while (distance(x1, y1, x2, y2) > 1e-6) {
        double x_mid = (x1+x2) / 2, y_mid = (y1+y2) / 2;
        double d1 = distance(x1, y1, xc, yc);
        double d2 = distance(x2, y2, xc, yc);
        if (d1 < d2) {
            x2 = x_mid;
            y2 = y_mid;
        } else {
            x1 = x_mid;
            y1 = y_mid;
        }
    }
    return std::min(distance(x1, y1, xc, yc), distance(x2, y2, xc, yc));
}


int main() {
    freopen("input.txt", "rt", stdin);
    freopen("output.txt", "wt", stdout);

    int x1, y1, x2, y2, x3, y3, xc, yc;
    scanf("%d %d %d %d %d %d %d %d", &x1, &y1, &x2, &y2, &x3, &y3, &xc, &yc);

    double d = min_distance(x1, y1, x2, y2, xc, yc);
    d = std::min(d, min_distance(x2, y2, x3, y3, xc, yc));
    d = std::min(d, min_distance(x1, y1, x3, y3, xc, yc));

    printf("%0.6lf", d);

    return 0;
}