s = gets.chomp
res = 0
cur = 0
tmp = ""
lst = []
for i in 0...s.length
  c = s[i]
  if c.ord == "ｗ".ord || c.ord == 33431
    if tmp!=""
      cur += 1
      if cur>res
        res = cur
        lst = [tmp.dup]
      elsif cur==res
        lst.push tmp.dup
      end
    end
  else
    if cur!=0
      tmp = ""
    end
    cur = 0
    tmp += c
  end
end
puts lst