func main()
	var n: int :: cui@inputInt()
	var map: dict<int, int> :: #dict<int, int>
	var ans: int :: 0
	var idx: int :: 0
	for i(1, n)
		var a: int :: cui@inputInt()
		do idx :: [idx, map.get(a, &)].max()
		do ans :: [ans, i - idx].max()
		do map.add(a, i)
	end for
	do cui@print("\{ans}\n")
end func