poj2507 Crossed ladders

#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
#define eps 1e-5
double l,r,mid,a,b,c,x,y,now;
bool judge(double k){
x=sqrt(a*a-k*k);
y=sqrt(b*b-k*k);
now=(x*y)/(x+y);
if(now-c>eps) return 0;
else return 1;
}
int main(){
while(scanf("%lf%lf%lf",&a,&b,&c)!=EOF){
l=0;r=max(a,b);
while(r-l>=eps){
mid=(l+r)/2.0;
if(judge(mid)) r=mid;
else l=mid;
}
printf("%.3lf\n",l);
}
return 0;
}