Could you help me solve this problem of stochastic processes in continuous time markov chains?

Problem:

Suppose S frogs play in a lake. When they are in the sun, they jump into the lake with rate = 1. When they are in the water, they jump into the sun with rate = 2. Be Xt the number of frogs in the sun in time t. Write matrix Q of this process. How to show that the stationary distribution is Binomial.

Thanks.