杭电2001

#include<stdio.h>

#include<string.h>

#include<stdlib.h>

#include<math.h>

int main()

{

    double x1,x2,y1,y2,s;

    while(scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2)!=EOF)

    {

         s=sqrt(((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));

         printf("%.2lf\n",s);

    }

   // system("pause");

    return 0;

}