# -*- coding: utf-8 -*-

W = 'ｗ'
readlines.each { |s|
  ans = {}
  s.size.times { |i|
    if s[i] != W && s[i+1] == W
      j = i
      t = ''
      while j >= 0 && s[j] != W
        t = s[j] + t
        j = j-1
      end
      j = i+1
      while j < s.size && s[j] == W
        j += 1
      end
      ans[j-i] = [] if ans[j-i].nil?
      ans[j-i] << t
    end
  }
  1000.downto(0) { |i|
    if ans[i]
      puts ans[i]
      break
    end
  }
}