G1.3 設 $f_{n+1}=\left\{\begin{array}{ll}f_{n}+3 & \text { 若 } n \text { 是雙數 } \\ f_{n}-2 & \text { 若 } n \text { 是單數 }\end{array}\right.$若 $f_{1}=60$, 求 $n$ 的最少可能值, 令當 $m \geq n$ 時, 満足 $f_{m} \geq 63$ 。
Let $f_{n+1}=\left\{\begin{array}{ll}f_{n}+3 & \text { if } n \text { is even } \\ f_{n}-2 & \text { if } n \text { is odd }\end{array}\right.$.
If $f_{1}=60$, determine the smallest possible value of $n$ satisfying $f_{m} \geq 63$ for all $m \geq n$.
$$
f_{2}=58, f_{3}=61, f_{4}=59, f_{5}=62, f_{6}=60, f_{7}=63, f_{8}=61, f_{9}=64, f_{10}=62, f_{11}=65, f_{12}=63 \cdots \cdots
$$

Now $f_{m} \geq 63$
The smallest possible value of $n$ is 11 .