Last one standing

This book is about these young adults who are all put into a team and expected to train and survive from the age of 6. The world outside of Argon is a mess, people killing people, everyone must fight to survive unless you are living in Argon. Argon is consumed of women who are pregnant and soldiers who protect said women, they used to be in the real world but were taken in so their Children could grow up to be soldiers. It's all a sick game really they just want the strongest person so they train them and send them out to see who lives and who dies.