#include<bits/stdc++.h>
using namespace std;
#define ll long long
int n;
int main()
{
	cin>>n;
	int flag;
	for(int i = 1 ; ; i++ )
	{
		if(4*(i-1)*(i-1)-4 >= n )
		{
			flag = i ;
			break;
		}
	}
	for(int i = 1 ; i < 1e3; i++ )
	{
		ll tt = i*i*4;
		if(tt==n)
		{
			double t =  i *1.0 * sqrt(2);
			printf("%.10llf",t);
		return 0;
		}
	}

	ll num = (flag-1)*(flag-1) + (flag-2)*(flag-2) ;
	double ans = sqrt(num);
	printf("%.10llf",ans);

 }