line = gets.chomp!
abort "format error" unless line=~/^\d+$/

n = line.to_i
abort "1<=N<=10" unless 1<=n && n<=10

cat = ""
n.times{
    line = gets.chomp!
    abort "format error" unless line=~/^[a-z]+$/
    abort "1<=len<=20" unless 1<=line.size && line.size<=20
    cat << line
}

abort "EOF" unless !gets

puts cat