x = int(input())
a = [2, 2, -1, -1, 2, -1, -1]
a = [[2, 2, -1, -1, 2, -1, -1][i % 7] for i in range(100)]
b = [sum(a[0:i+1]) for i in range(100)]
c = [sum(list(map(abs, a[0:i+1]))) for i in range(100)]
x_index = b.index(x)
print(c[x_index])