n = int(input())
p = []
# the number of relationships of influence
for i in range(n):
    # x: a relationship of influence between two people (x influences y)
    x, y = [int(j) for j in input().split()]
    p.append((x,y))

length = 0
print(p, file=sys.stderr)
for x,y in p:
    p1 = list(p)
    p1.remove((x,y))
    j = [x,y]
    for obj in p1:

        if j[0] == obj[-1]:
            j.insert(0,obj[0])
        elif j[-1] == obj[0]:
            j.append(obj[-1])
    print(j, file=sys.stderr)
    if len(j) > length:
        length = len(j)


print(length)