测试数据很弱，double就可以过了

题目：​​http://acm.hdu.edu.cn/showproblem.php?pid=2001​​

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