Paragraph- Sent 1: Ludo Decker and Anna Gotzlowski have been living together for two years .
Sent 2: Everyday routine has set in , with Ludo neglecting his household responsibilities much to Anna 's dislike , while he is in turn annoyed by her constant complaining .
Sent 3: When Ludo runs into his former lover Marie in the disco , and Anna 's old boyfriend Ralf comes to stay in their flat for a few days , the young couple faces serious jealousy and doubt in their relationship .
Sent 4: Anna secretly reads Ludo 's phone messages , while he in turn stumbles upon `` The List '' , an account of Anna 's former lovers -- including Ralf , who scores better than Ludo does .
Sent 5: After a number of provocations , Ludo beats Ralf in a restaurant , and angrily leaves Anna .
Sent 6: Even though the two still strongly care for each other , they end up sleeping with their respective ex-lovers .
Sent 7: Ralf confesses that he never stopped loving Anna , but she rejects him and tells Ludo what happened .
Sent 8: Even though Ludo has cheated on her as well , he angrily argues that she herself told him that , unlike men , women do not actually sleep with someone without feelings being involved .
Sent 9: Anna begs him to come home , but he only says that he has no home any more , and leaves .
Sent 10: Meanwhile , Ludo 's best friend Moritz desperately tries to get more successful with women , and ends up in a number of absurd situations .
Sent 11: In the end , he meets a young and beautiful sex-addict named Lana .
Sent 12: After a few weeks , Anna receives a letter from Ludo , who has traveled back to the place where they spent their first and only vacation together . 
Question: How long had Ludo and Anna been living together before Ralf came to stay with them for a few days? 
Incorrect Answer: three years.