the horizon (1 &lt;= A_i &lt; B_i &lt;= 1,000,000,000) and has height H_i (1 &lt;= H_i &lt;= 1,000,000,000). Determine the area, in square units, of the aggregate silhouette formed by all N buildings. </span></p>
<p><span style="font-size: medium">N个矩形块，交求面积并.</span></p></div></div></div></div><div class="row"><div class="column"><h4 class="ui top attached block header">输入格式</h4><div class="ui bottom attached segment font-content"><div style="position: relative; overflow: hidden