Consider the set S of all integers between and including 1000 and 99999. Call two integers x and y in S to be in the same equivalence class if the digits appearing in x and y are the same. For example, if x=1010, y=1000 and z=1201, then x and y are in the same equivalence class, but y and z are not. Find the number of distinct equivalent classes that can be formed out of S.