#include <bits/stdc++.h>
using namespace std;
double a,b,c,r;
double m(double x1){
	double fx1=a*x1*x1+b*x1+c,k=2*a*x1+b;
	double b=fx1-k*x1;
	return 0-(b/k);
}
signed main(){
	cin>>a>>b>>c;
	for(int i=0;i<10000;i++){
		r=m(r);
	}
	printf("%.5lf",r);
	return 0;
}