#include<iostream>
using namespace std;
int main(){
	double x;
	cin>>x;
	double l=0,r=x;
	while(r-l>1e-8){
		double mid=(l+r)/2;
		if(mid*mid>=x)r=mid;
		else l=mid;
	}
	
	cout<<l<<endl;
	return 0;
}