#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
	double x;
	cin >> x;
	double a1 = x, a2 = (a1 + x/a1)/2.0;
	while (abs(a1-a2) >= 0.000001) {
		a1 = a2;
		a2 = (a1 + x/a1)/2.0;
	}
	printf("%.3f\n", a2);
	return 0;
}