A young man tried to marry the princess, but the king found out and offered him a sporting chance. He would place two slips of paper in a box, one marked Death, and one marked Princess. To decide his fate, the young man would be blindfolded and chose one paper. The young man found out that the king didn't want him to marry the princess, therefore intending to mark both slips as Death.
The young man got the princess in spite of this.
How?