What would you do if you were excluded from conversation when you go out with just two others?

Not long ago i had a horrible experience whereby i went to a dinner with just two others. They both engaged in a big conversation & i was totally excluded. i could not get a word in edge-ways. I did make an effort to partipate but it was useless. Basically one person just addressed the other the entire time & i was left there staring around me. It was sooo uncomfortable i wanted to leave. What should i have done? It was just such a horrible experience. :/