#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import random
import statistics

EXP_TIMES = 50000


def roll_dice(k):
    n = 0
    s = 0
    while s < k:
        d = random.randint(1, 6)
        n += 1
        s += d
    return n


def get_expectation(k):
    return statistics.mean(float(roll_dice(k)) for i in range(EXP_TIMES))


def main():
    print(get_expectation(int(input())))

if __name__ == "__main__":
    main()