Suppose we take some water in a container and seal it. Now we place it on a heater, the water starts boiling and converts into vapour. Now if we allow the container to cool down for some time and then open seal. The amount of water we get:
Will be equal to the initial amount
As the water does not escape from the container (the container is sealed), it only gets converted into vapour and then back into liquid form when cooled. So the amount of water will be equal to the initial amount.