#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define pb push_back
int dy[]={0, 0, 1, -1, 1, 1, -1, -1};
int dx[]={1, -1, 0, 0, 1, -1, -1, 1};

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define mp make_pair
#define fi first
#define sc second
int k;
double saiki(int x){
    if(x >= k)
        return 0.0;
    double sum = 1.0;
    FOR(i,1,7)
        sum += saiki(x + i) / 6.0;
    return sum;
}
int main(){
    scanf("%d",&k);
    printf("%lf\n",saiki(0));
    return 0;
}