This game is adopted from episode six of the Survivor Thailand television series that aired in fall 2002. Two players alternate in taking turns to remove some number of flags from a field with 31 flags. Each time it is a player’s turn, he may choose to remove 1, 2, 3, or 4 flags. The player to remove the last flag is the winner. Suppose you are the player to move first, how do you play the game to guarantee yourself a win? Please explain how you find the winning strategy.