import java.io.*; class Main{ static final PrintWriter out=new PrintWriter(System.out); public static void main(String[] args) throws IOException{ BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); String line=""; while((line=br.readLine())!=null&&!line.isEmpty()){ int n=Integer.parseInt(line); double[] dp=new double[n+5]; dp[n-1]=1; for(int i=n-2;i>=0;i++){ dp[i]=dp[i+1]/6+dp[i+2]/6+dp[i+3]/6+dp[i+4]/6+dp[i+5]/6+dp[i+6]/6+1; } out.printf("%.20f",dp[0]); out.flush(); } } }