Need help with expected value

May 2010
Suppose that a particle starts at the origin of the real line and moves along the line injumps of one unit. For each jump, the probability is p that the partical will jump one unit to the left and the probability is (1-p) that the particle will jump one unit to the right.
Find the expected value of the position of the particle after n jumps.

can anyone help me with this one?????