#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
int main(){
  double a;
  while(cin >> a){
    double s[11] ={}, ans = 0;
    for(int i = 1; i <= 10; i++){
      int si = 0, bo = 0;
      if(i == 1) s[i] = a;
      else if(i % 2 == 0){
        si = pow(2, i/2);
        bo = pow(3, (i/2) - 1);
        s[i] = a * (si / bo);
      }
      else{
        si = pow(2, i/2);
        bo = pow(3, i/2);
        s[i] = a * (si / bo);
      }
      ans += s[i];
    }
    cout << fixed << setprecision(8) << ans << endl;
  }
}