Job search problem, or the secretary problem is one application of the optimal stopping problem, and the optimal stopping strategy is for a given sample size n, we pass over the first k offers, and stop at the first offer which is better than all the preceding ones. Here k/n is approximately 1/e. However in reality we don't always know the sample size in advance, but can assume it's a random variable follows certain distribution. We find the optimal stopping strategy in this situation.