#!usr/bin/env python3
from collections import defaultdict, deque
from heapq import heappush, heappop
from itertools import permutations, accumulate
import sys
import math
import bisect
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def I(): return int(sys.stdin.readline())
def IR(n):
    return [I() for _ in range(n)]
def LIR(n):
    return [LI() for _ in range(n)]

sys.setrecursionlimit(1000000)
mod = 1000000007

def main():
    n = I()
    l = 0
    r = 10**10
    while l+1 < r:
        m = (l+r) >> 1
        s = n+(m//7)
        if s <= m:
            r = m
        else:
            l = m
    print(r)
    return


if __name__ == "__main__":
    main()