stable marriage alteration, searching for infinte loop with 6 people

Question

given is the following algorithm: we choose an initial assignment of man^woman, so that every man is engaged to exactly one woman and vice versa. now if there's a man m that prefers a woman f' to his actual partner f, and a woman f that prefers man m to her actual partner m', then m and f get engaged, and m' and f' get engaged. this is repeated until no changes occur. now i'm looking for a case with 3 men and 3 women that never ends. what would the preferences of every man and woman has to be so that the algorithm never ends? Thanks for your time!