X = int(input())
a = m = Y = 0
n = 1
while X != a:
    m = n % 7
    if m == 1 or m == 2 or m == 5:
        a += 2
        Y += 2
    elif m == 3 or m == 4 or m == 6 or m == 0:
        a -= 1
        Y += 1
    if X == a:
        print(Y)
    n += 1