#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

int main()
{
    double result = 768*sqrt(2-sqrt(2+sqrt(2+sqrt(2+sqrt(2+sqrt(2+sqrt(2+sqrt(2+sqrt(2+sqrt(2+1))))))))));
    
    setprecision(15);
    cout << result <<endl;
}