def Main():
    a=2
    b=-1
    walk=[a,a,b,b,a,b,b]
    now=0
    count=0
    ans=0
    x=int(input())
    while True:
        count+=walk[now%7]
        ans+=abs(walk[now%7])
        now+=1
        if count==x:
            break
    print(ans)
Main()