A, B, C, D, E and F are nonzero numbers. How many different mathematical expressions can you obtain by placing a mathematical operator (one of addition, subtraction, multiplication or division operator) into the blank squares, and using any number of parentheses?

Two expressions are not different if they produce the same result.
Example: (AxB)/C/(D-E)-F and (AxB)/(Cx(D-E))-F are not different expressions.

Notes:
*Multiplication and division have priority over addition and subtraction.
*Assume that there won't be any zero divisions during the operations.