#include<bits/stdc++.h>
using namespace std;
#define MOD (long long)(1e9+7)
typedef long long int ll;
typedef unsigned long long int ull;

ll modularExponentiation(ll x, ll y, ll  p){
  ll res = 1;
  x = x % p;
  while (y > 0){
      if (y & 1) res = (res*x) % p;
      y = y>>1;
      x = (x*x) % p;
  }
  return res;
}

bool isPrime(ll n){
    if (n <= 1)  return false;
    if (n <= 3)  return true;
    if (n%2 == 0 || n%3 == 0) return false;
    for (int i=5; i*i<=n; i=i+6)
        if (n%i == 0 || n%(i+2) == 0)
           return false;
    return true;
}

int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ll T=1;
  // cin>>T;
  for(int _case=0;_case<T;_case++){
    double n;
    cin>>n;
    cout<<2*double(104348/33215.)*n;
  }
  return 0;
}
