John is playing a game in which he tries to obtain the highest number possible. He must put the symbols , $\times$, and - (plus, times, and minus) in the following blanks, using each symbol exactly once:\[ 2 \underline{\phantom{8}} 4 \underlined phantom{8}} 6 \underline{\hphantom{8}} 8. \]John cannot use parentheses or rearrange the numbers. What is the highest possible number that John could obtain