789 B | 789 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
BLANK = " "
#inp = input
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def f(a, l):
ret = 0
for i, j in l:
X = a.index(i)
Y = a.index(j)
if (X == 0 and Y == 2) or (X - 1 == Y):
ret += 1
return ret
def solve():
n = ii()
l = [mii() for _ in range(n)]
ans = 0
k = [[1, 2, 3],[1 ,3, 2],[2, 1, 3],[2, 3, 1],[3, 1, 2],[3, 2, 1]]
for i in k:
ans = max(ans, f(i, l))
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()