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

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

#define mygc(c) (c)=getchar_unlocked()
#define mypc(c) putchar_unlocked(c)

void reader(int *x){int k,m=0;*x=0;for(;;){mygc(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){mygc(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}

double mem[1000], *dp;

int main(){
  int i, j, k, N;

  dp = mem + 10;
  REP(i,-6,1) dp[i] = 0;
  REP(i,1,21){
    dp[i] = 1;
    rep(j,6) dp[i] += dp[i-6+j]/6;
  }

  reader(&N);
  printf("%.15f\n",dp[N]);

  return 0;
}