1084: 计算两点间的距离（多实例测试）

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