import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
#from collections import defaultdict 
#from collections import deque
#import copy
#import math
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
#MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

def main():
    X = int(input())
    ans = 0
    v = 0
    A = [0,1,4]
    for i in range(10000):
        if i%7 in A:
            v += 2
            ans += 2
        else:
            v -= 1
            ans += 1
        if v == X:
            print(ans);exit()



if __name__ == '__main__':
    main()