class Step:
    l = []
    d = {}
    limit = 0

    def __init__(self, num):
        self.limit = 5 * num
        self.l = [0] * self.limit
        self.l[0] = 1

    def __getitem__(self, key):
        if self.limit > key:
            return self.l[key]
        else:
            return self.d.setdefault(key, 0)

    def __setitem__(self, key, value):
        if self.limit > key:
            self.l[key] = value
        else:
            self.d[key] = value



def collatz_step(x, path):
    global steps
    if steps[x - 1]:
        foot = steps[x - 1] + 1
        while path:
            steps[path.pop() - 1] = foot
            foot += 1
        return
    else:
        path.append(x)
        if x % 2:
            collatz_step(3 * x + 1, path)
        else:
            collatz_step(x // 2, path)

def collatz_max(num):
    global steps
    for x in range(1, num + 1):
        if steps[x - 1]:
            continue
        collatz_step(x, [])
    return steps.l.index(max(steps.l[:num])) + 1


limit = 1000000
steps = Step(limit)
print(collatz_max(limit))