is there some way to create unique number from 2 positive integer numbers? Result must be unique even for these pairs: 2 and 30, 1 and 15, 4 and 60. In general, if I take 2 random numbers result must be unique(or with very high probability unique)

Thanks a lot

EDIT: calculation is for computer program,so computational complexity is important

The sort of function you are looking for is often called a pairing function. 

A standard example is the Cantor pairing function $\mathbb{N}\times\mathbb{N}\rightarrow\mathbb{N}$, given by:
$\pi(a,b) = \frac{1}{2}(a+b)(a+b+1) + b$.

You can find more information here: http://en.wikipedia.org/wiki/pairing_function
