A computational problem is generally defined in terms of its action on any valid input. Examples of problems might be "given an integer "n", determine whether "n" is prime", or "given two numbers "x" and "y", calculate the product "x"*"y"". As the inputs get bigger, the amount of computational resources needed to solve a problem will increase. Thus, the resources needed to solve a problem are described in terms of asymptotic analysis, by identifying the resources as a function of the length or size of the input. Resource usage is often partially quantified using Big O notation.