Try this:
timeToClimb = 1;
timeToStay = 2;
initialY = 243;
positionY = initialY - 5 * Math.floor(time / (timeToClimb + timeToStay));
t = time % (timeToClimb + timeToStay);
[432, linear(t, 0, timeToClimb, positionY, positionY - 5)]
Xinlai Ni
Software Engineer, Google Inc.