So when the slope is zero, we deal with phase changes. And here all energy input goes into increasing potential energy of the system. No change in kinetic energy is observed. And so the change in temperature in both cases is zero. When we talk about going from this guy to this guy or from this guy to this guy, the intermediate phases between the phase changes, we talk about energy input that goes into increasing kinetic energy of the system because kinetic energy of the system is what increases temperature. Because we want to go from zero to 100 and from negative 60 to zero.