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

int main(void) {
    ll N;
    cin >> N;
    double dp[N+1][7];
    dp[1][0] = 0;
    dp[1][1] = 1;
    for (int i=2; i<=6; i++) dp[1][i] = 0;
    for (int i=2; i<=N; i++) for (int j=1; j<=6; j++) {
        dp[i][j] = ( (dp[i-1][j] * j) + (dp[i-1][j-1] * (7-j)) ) / 6;
    }
        printf("%.10f\n",dp[N][6]);
    return 0;
}