n = int(input())
l = [*map(int, input().split())]
flag = [0, 0, 0, 0, 0]
d = [
[0, 1, 2],
[0, 1],
[1, 2],
[0, 2],
[2],
]
for i in l:
for j in range(5):
if flag[j] >= len(d[j]):
continue
if i == d[j][flag[j]]:
flag[j] += 1
print(max(flag))