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

typedef struct point {
    double x;
    double y;
} Point;
//거리함수
double get_dist(double time,Point a,Point b,Point c,Point d) {
    //민호
    double x1= a.x + (b.x-a.x) * time;
    double y1= a.y + (b.y-a.y) * time;
    //강호
    double x2= c.x + (d.x-c.x) * time;
    double y2= c.y + (d.y-c.y) * time;
    
    return sqrt(pow(x2-x1,2) + pow(y2-y1,2));
}

int main() {
    Point a,b,c,d;
    scanf("%lf %lf %lf %lf %lf %lf %lf %lf",&a.x,&a.y,&b.x,&b.y,&c.x,&c.y,&d.x,&d.y);
    //시간 0부터 1까지
    double low=0.0 ,high =1.0;
    //삼분탐색
    for(int i=0; i<100; i++) {
        double m1=(2.0*low+high)/3.0;
        double m2=(low+2.0*high)/3.0;

        if(get_dist(m1,a,b,c,d) < get_dist (m2,a,b,c,d)) {
            high = m2;
        } else {
            low = m1;
        }
    }
    printf("%.10f\n", get_dist(low,a,b,c,d));
    return 0;
}