At the local grocery store, there is a very strict code that the shop assistants must adhere to. When a customer asks for a certain number of potatoes, he or she must first take potatoes from the crate containing bags of 3 potatoes only and then take potatoes from the crate containing bags of 5 potatoes only. The shop assistant cannot come back to the crate with bags of 3 potatoes. He/she can choose take to as many bags from either crate provided there is at least one taken from each sack.

One day, a customer visited the store and told the shop assistant that he would like X number of potatoes. The shop assistant figured out how he should give the customer the exact number of potatoes he had requested but he discovered there was only one way to do this.

What is X? Find all possible solutions.