---

def f(n):
    r = ''
    while n>0:
        r = str(n%2)+r
        n = n//2 
    return r
t = []
for n in range(1,1000):
    r = f(n)
    if r.count('1')%2==0:
        r='10'+r[2:]+'0'
    else:
        r='11'+r[2:]+'1'
    r=int(r,2)
    if r<=19:
        t.append(n)
print(max(t))