<span class="hljs-comment">// 1.11</span>
f2(<span class="hljs-number">1.5555</span>)           <span class="hljs-comment">// 1.56</span>
f2(<span class="hljs-number">10.5555</span>)          <span class="hljs-comment">// 10.6</span>
f2(<span class="hljs-number">100.5555</span>)         <span class="hljs-comment">// 101</span>
f2(<span class="hljs-number">1000.5555</span>)        <span class="hljs-comment">// 1K</span>
f2(<span class="hljs-number">1000000.5555</span>)     <span class="hljs-comment">// 1M</s