#include <iostream>
#include <algorithm>
#include <cmath>
#define lc (d<<1)
#define rc (d<<1|1)
#define m (l+r>>1)
#define N 100005
using namespace std;
//s(x^2 - d^2) * s(y^2 - d^2) = c * ( s(x^2 - d^2) + s(y^2 - d^2) );
double x,y,c;
double s(double d) {
	return 1-c/sqrt(x*x-d*d)-c/sqrt(y*y-d*d);
}
int main() {
	double d,mid;
	while(cin>>x>>y>>c) {
		d = min(x,y);
		double l = 0;
		double r = d;
		while(l<=r) {
			mid = (l+r)/2;
			if(s(mid)>0){
				l=mid+1e-10;
			}else r=mid-1e-10;
			
		}
		printf("%.3f\n",mid);
	}
	return 0;
}