#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
double x, y, c;
bool check(double t){
    double hx = sqrt(x * x - t * t);
    double hy = sqrt(y * y - t * t);
    double hc = (hx * hy) / (hx + hy);
    if(hc >= c)     return true;
    return false;
}
int main(){

    cin >> x >> y >> c;
    double l = 0, r = 3000;
    double mid;
    while(r - l >= 1e-4){
        mid = (l + r) / 2;
        if(check(mid))  l = mid;
        else    r = mid;
    }
    printf("%.3lf", l);
    return 0;
}