The Game of Death Part I. The gangster leader selects an agent and forces the selected agent to play another **Game of Death: Russian Roulette**. The gangster leader puts two bullets in consecutive order in an empty six-round revolver, spins it, and points the muzzle at agent's head. The rules of the game are:

- In each chance, the agent can choose either he wants to spin revolving cylinder again or not.
- If the agent can survive from four times chance, he and the other four agents will be released. If not, the rest will be killed.

Assuming that the agent uses **the best strategy**. What is the probability that the agent will survive?

**Note:** Your answer must be in the interval $[0,1]$.