What do Peeta and Katniss do to outsmart the Gamemakers? Do they succeed or fail?

Peeta and Katniss both hold some nightlock berries in their hands. Katniss instructed that when she counted to three, they would each put the berries in their mouths and swallow, since neither wants to kill one another. Nightlock berries are extremely poisonous, and they would kill you even before they reached your stomachs. Before they swallowed, however, the gamemakers stopped the game and declared them both winners.