everyone = []
gets.chomp.to_i.times { everyone << gets.chomp.split.map(&:to_i)[1..] }

def is_empty(array)
    array.each {|vec| return false if not vec.size == 0 }
    true
end

order = []
while (not is_empty(everyone))
    everyone.each {|line|
        customer = line.shift
        order << customer if customer
    }
end
puts order.join ' '