# Hexadecimals without Letters

**Number Theory**Level 5

Find the least upper bound of \(S\).

Details:

For example, \(1.45 \in S\) because its hexadecimal expansion is \(1.7\overline{3}_{16}\), which only consists of the digits \(1,3,7\). However \(240 \not \in S\) because its hexadecimal expansion is \(f0_{16}\) which contains an \("f"\).

Please write the answer in base 10, not 16.