

<span class="comment">// ...</span>

<span class="keyword">int</span> <span class="identifier">user_id</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cin</span> <span class="special">&gt;&gt;</span> <span class="identifier">user_id</span><span class="special">;</span>

<span class="identifier">People</span><span class="special">::</span><span class="identifier">map_by</span><span class="special">&lt;</span><span class="identi