> #include <stdio.h>
> #include <math.h>
> 
> #define  M 1e-5
> 
> int   main ()
> {
>     double  x,y,c,t;
> 
> label:while(scanf("%lf%lf%lf",&x,&y,&c)==3)
>     {
>        double  mid,low,high,sum;
>        if(x<y)
>            t=x,x=y,y=t;
>        if(c>=y)
> 			goto  label;
>        low=0,high=y;
> 	   do
> 	   {
>             mid=(low+high)/2;
>             sum=c/sqrt(y*y-mid*mid)+c/sqrt(x*x-mid*mid);
> 
>             if(sum>1)
>                 high=mid;
>             else  if(sum<1)
>                 low=mid;
>             else
>                 goto  lza;
>         }while(fabs(sum-1)>M && low+M<high);
> 
> lza:    printf("%.3lf\n",mid);
>     }
> }
> 
> 
> 谢谢了哈....