print((function (h, n)
	function count(r)
		for _,v in pairs(h) do if v == 1 then r = r + 1 end end
		return math.floor(r / 4)
	end
	for _=1,io.stdin:read("*n")*3 do
		local t = io.stdin:read("*n")
		if h[t] == 1 then h[t],n = 0,n+1 else h[t] = 1 end
	end
	return n + count(0)
end)({}, 0))