The least common denominators could be for example:
Both of you are in a dispute and would rather be somewhere else.
Both of you want to find a peaceful solution.
Both of you have children and want to be a good example for them.
Both of you are hungry, excited, enthusiastic… and after a rest you will be able to concentrate on finding a great solution easily.
Both of you are human – somehow…, or pretend to be.
Both of you will learn from this situation and will do it better next time.
Usually you will find out that the least common denominator is greater than you thought before - and a helpful tool to find the best solution.