杭电2001----计算两点间的距离

#include<stdio.h>
#include<math.h>
int main()
{
    double x1,x2,y1,y2;
    while(~scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2))
        printf("%.2lf\n",sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));
    return 0;
}