Koh-Lanta.

Fourteen to eighteen contestants have to survive on an uninhabited island for 40 days (20 days in the special editions). It's up to them to find food to accompany the meagre ration of rice provided at the start of the adventure. They have to build a shelter to protect themselves from the elements (bad weather, insects, etc.) and maintain the fire that they managed to build or that they won in the first comfort test.