The dimensional formula of 1/2 ε_o E^2 ( ε_o= permittivity of vacuum and E= electric field) is M^a L^b T^c. The value of 2 a-b+c= ____.

The dimensional formula of $\displaystyle \frac{1}{2} \epsilon_o E^2$ ( $\displaystyle \epsilon_o=$ permittivity of vacuum and $\displaystyle E=$ electric field) is $\displaystyle M^a L^b T^c$. The value of $\displaystyle 2 a-b+c=$ $\displaystyle \_\_\_\_$.