AtCoder AGC 028 A

agc028-a.rb

n, m = gets.chomp.split(" ").map(&:to_i)

s = gets.chomp
t = gets.chomp

l = n.lcm(m)

x = Hash.new(nil)

n.times do |i|
  j = i * (l / n)
  x[j] = s[i]
end

m.times do |i|
  j = i * (l / m)
  if !x[j].nil?
    if x[j] != t[i]
      puts -1
      exit
    end
  end
end

puts l