m = gets.to_i
as = (1..m).map { gets.chomp }
n = gets.to_i
bs = (1..n).map { gets.chomp }

adic = {}
bdic = {}
as.each { |a| adic[a[0]] = a }
bs.each { |b| bdic[b[0]] = b }

('A'..'Z').each do |head|
  next unless adic[head]
  next unless bdic[head]
  abuf = adic[head]
  bbuf = bdic[head]

  aused = 1

  while abuf.size != bbuf.size
    if abuf.size > bbuf.size
      head = abuf[bbuf.size]
      bbuf += bdic[head]
    else
      head = bbuf[abuf.size]
      abuf += adic[head]
      aused += 1
    end
  end

  next if abuf != bbuf

  if aused < m
    p -1
    break
  end

  puts abuf
  break
end