N = gets.to_i
S = gets.split.map(&:to_i)

dp1 = Array.new(N + 1, -100_000_000)
dp2 = Array.new(N + 1){ Array.new(N + 1, -100_000_000) }
S[0,2].sort.tap do |x,y|
  dp1[x] = dp1[y] = dp1[0] = 0
  dp2[x][y] = 0
end
base = 0
q = []

(1 ... N).each do |i|
  a,b,c = S[3 * i - 1, 3].sort
  if a == c
    base += 1
    next
  elsif a == b
    (1 .. N).each do |x|
      next if dp2[x][a] < 0 && dp2[a][x] < 0
      if x < a
        q << [x, c, dp2[x][a] + 1] if dp2[x][c] < dp2[x][a] + 1
      elsif x < c
        q << [x, c, dp2[a][x] + 1] if dp2[x][c] < dp2[a][x] + 1
      else
        q << [c, x, dp2[a][x] + 1] if dp2[c][x] < dp2[a][x] + 1
      end
    end
    if dp2[c][c] >= 0
      q << [a, a, dp2[c][c] + 1]
    end
  elsif b == c
    (1 .. N).each do |x|
      next if dp2[x][c] < 0 && dp2[c][x] < 0
      if x < a
        q << [x, a, dp2[x][c] + 1] if dp2[x][a] < dp2[x][c] + 1
      elsif x < c
        q << [a, x, dp2[x][c] + 1] if dp2[a][x] < dp2[x][c] + 1
      else
        q << [a, x, dp2[c][x] + 1] if dp2[a][x] < dp2[c][x] + 1
      end
    end
    q << [c, c, dp2[a][a] + 1] if dp2[a][a] >= 0 && dp2[c][c] < dp2[a][a] + 1
  else
    q << [b, c, dp2[a][a] + 1] if dp2[a][a] >= 0 && dp2[b][c] < dp2[a][a] + 1
    q << [a, c, dp2[b][b] + 1] if dp2[b][b] >= 0 && dp2[a][c] < dp2[b][b] + 1
    q << [a, b, dp2[c][c] + 1] if dp2[c][c] >= 0 && dp2[a][b] < dp2[c][c] + 1
  end
  
  q << [a, b, dp1[0]]
  q << [a, c, dp1[0]]
  q << [b, c, dp1[0]]

  (1 .. N).each do |x|
    next if dp1[x] < 0
    [a,b,c].each do |y|
      if x < y
        q << [x, y, dp1[x]] if dp2[x][y] < dp1[x]
      else
        q << [y, x, dp1[x]] if dp2[y][x] < dp1[x]
      end
    end
  end
  
  until q.empty?
    a,b,v = q.shift
    if dp2[a][b] < v
      dp2[a][b] = v
      dp1[0] = v if dp1[0] < v
      dp1[a] = v if dp1[a] < v
      dp1[b] = v if dp1[b] < v
    end
  end
end
puts base + [dp1[0], dp2[S[-1]][S[-1]] + 1].max
