X=int(input())

x=0
T=0
mode=0
S=[1,1,0,0,1,0,0]
while True:
    if S[mode]==1:
        x+=2
        T+=2
    else:
        x-=1
        T+=1

    if x==X:
        break

    mode=(mode+1)%len(S)

print(T)