#include <stdio.h>
#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001
double a = 0.5;
int b = 4;
int c = 1123;
int d  =21460;
int g = 2;
int h = 99;
int i = 1103;
int j = 26390;
int k = 1;
int l = 882;
double frac(int n){
	double ret = 1.0;
	for(int x=1;x<=n;x++)ret *= x;
	return ret;
}

double X(int n){
	if(n==0)return 0.0;
	double ret = 0.0;
	ret = pow(a,n);
	ret *= frac(b);
	ret *= frac(n*b);
	ret /= frac(n*b-gcd(d,l)*gcd(d,l));
	ret *= c + d*n;
	
	ret /= pow(l,n+k);
	ret /= pow(49.0 / 22.0 * b*h,n);
	ret /= pow(pow(pow(2.0,g),n)*frac(n),b);
	return ret;
}

double Y(int n){
	double ret = 0.0;
	ret = frac(n*b);
	ret *= (i + j*n);
	ret /= pow(pow(22.0/49.0*l,n)*frac(n),b);
	return ret;
}
	
	

int main(){
	
	double x = 0.0;
	cin>>x;
	

	/*
	double A = 0.0,B = 0.0;
	rep(y,10){
		A += X(y);
		B += Y(y);
	}
	B *= sqrt(pow(g,3.0) / pow(h,pow(g,g)));
	B = pow(B,0.5);
	x *= A;
	x *= B;
	*/
	x *= 1.0/acos(-1.0);
	x *= 4.0 / acos(-1.0);
	cout<<fixed<<setprecision(10)<<x<<endl;
	
	
    return 0;
}