A proton moves at 3.3 x 10^5 m/s in the horizontal direction. It enters a uniform vertical electric field with a magnitude of 4 x 10^3 N/C. Ignoring any gravitational effects, find its vertical displacement during the time interval in which it travels 5.00 cm horizontally. (mp = 1.67 x 10^-27 kg, q = 1.6 x 10^-19 C) Express your answer in the unit of millimeter.