#using : utf-8
#encoding : utf-8

s = gets.chomp

ans = 0

len = 0
con = false

dot = "ｗ"

arr = Array.new(s.length)

for i in 0...s.length do
	arr[i] = -1
	if s[i] == dot then
		if con == true then
			len += 1
			ans = [ans, len].max
		else
			con = true
			len = 1
			ans = [ans, len].max
		end
		arr[i] = 0
		arr[i-len+1] = len
	else
		len = 0
		con = false
	end
end


for i in 1...s.length do
	if arr[i] > 0 then
		if arr[i] == ans then
			x = i-1
			while x > 0 && s[x-1] != dot do
				x -= 1
			end
			puts s[x, i-x]
		end
	end
end

if ans == 0 then
	puts ""
end