555 = 185*3 = (61*3 + 2)*3 = ((20*3 + 1)*3 + 2)*3 + 0 = (((6*3+2)*3 + 1)*3 + 2)*3 + 0 = ((((2*3 + 0)*3+2)*3 + 1)*3 + 2)*3 + 0 = 202120(3)