#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair< int, int > pii;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef vector< pii > vp;
typedef vector< vp > vvp;
typedef vector< string > vs;
typedef vector< double > vd;
typedef vector< vd > vvd;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;

int K;

void init(){
  cin >> K;
}

vd dp;

void preprocess(){
  dp = vd( K );
  for( int i = 0; i < 100000; ++i )
    for( int j = 0; j < K; ++j ){
      double s = 0.0;
      for( int k = 1; k <= 6; ++k ){
        if( j + k < K )
          s += dp[ j + k ] / 6;
        if( j + k > K )
          s += dp[ 0 ] / 6;
      }
      dp[ j ] = s + 1.0;
    }
}

void solve(){
  cout << fixed << setprecision( 6 ) << dp[ 0 ] << endl;
}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}