Mathematics Question from JEE Main 2023 · 30 January, Shift 1

Let $S = \{1, 2, 3, 4, 5, 6\}$. Then the number of one-one functions $f: S \to P(S)$, where $P(S)$ denotes the power set of $S$, such that $f(n) \subset f(m)$ where $n < m$, is _____.