n = int(input())
lt = []
for _ in range(n):
    lt.append(list(map(int, input().split())))
lt.sort()
g = [1] * n
for i in range(n):
    for j in range(i):
        if lt[i][1] > lt[j][1]:
            g[i] = max(g[i], g[j]+1)
print(max(g))