#!/bin/python3

import math
import os
import random
import re
import sys

#
# Complete the 'viralAdvertising' function below.
#
# The function is expected to return an INTEGER.
# The function accepts INTEGER n as parameter.
#

class People:
    def __init__(self, received):
        self.received = received
        self.liked = 0
    
    def calculate_likes(self):
        self.liked = self.received // 2
        return self.liked
    
    def get_next_day_receivers(self):
        return self.liked * 3


class Day:
    def __init__(self, day_number, received):
        self.day_number = day_number
        self.people = People(received)
    
    def process_day(self):
        likes = self.people.calculate_likes()
        next_day_receivers = self.people.get_next_day_receivers()
        return likes, next_day_receivers


class AdvertisingCampaign:
    def __init__(self, total_days):
        self.total_days = total_days
        self.cumulative_likes = 0
        self.initial_receivers = 5
    
    def run_campaign(self):
        current_receivers = self.initial_receivers
        for day_number in range(1, self.total_days + 1):
            day = Day(day_number, current_receivers)
            likes, next_day_receivers = day.process_day()
            self.cumulative_likes += likes
            current_receivers = next_day_receivers
        return self.cumulative_likes


def main():
    n = int(input())
    campaign = AdvertisingCampaign(n)
    total_likes = campaign.run_campaign()
    print(total_likes)


if __name__ == "__main__":
    main()