<BR>/**<BR> &amp;#pku2431.cpp<BR> @author Eastsun<BR> @version 1.0 2007/10/14<BR>*/<BR>#include&lt;iostream&gt;<BR>#include&lt;queue&gt;<BR>#include&lt;vector&gt;<BR>#include&lt;algorithm&gt;<BR>#include&lt;functional&gt;<BR>using namespace std;</P> <P>struct Stop{<BR> Stop(int d,int f){<BR> dis =d;<BR> fuel =f;<BR> }<BR> int dis;<BR> int fuel;<BR>};<BR>struct CmpByDis:public binary_function&lt;Stop,Stop,bool&gt;{<BR> bool operator()(const Stop&amp; s1,const Stop&amp; s2)const{<BR> return s1.dis &gt;s2.dis;<BR> }<BR>};<BR>struct CmpByFuel:public binary_function&lt;Stop,Stop,bool&gt;{<BR> bool operator()(const Stop&amp; s1,const Stop&amp; s2)const{<BR> return s1.fuel &lt;s2.fuel;<BR> }<BR>};<BR>int main(){<BR> int n;<BR> cin&gt;&gt;n;<BR> vector&lt;Stop&gt; vec;<BR> for(int i =0;i &lt;n;i ++){<BR> int d,f;<BR> cin&gt;&gt;d&gt;&gt;f;<BR> vec.push_back(Stop(d,f));<BR> }<BR> int dist,fuel,count =0;<BR> cin&gt;&gt;dist&gt;&gt;fuel;<BR> sort(vec.begin(),vec.end(),CmpByDis());<BR> priority_queue&lt;Stop,vector&lt;Stop&gt;,CmpByFuel&gt; queue;<BR> vector&lt;Stop&gt;::iterator itr =vec.begin();<BR> for(;;){<BR> for(;itr!=vec.end()&amp;&amp;fuel&gt;=dist -(*itr).dis;itr ++)<BR> queue.push(*itr);<BR> if(queue.empty()){<BR> cout&lt;&lt;-1&lt;&lt;endl;<BR> break;<BR> }<BR> if(fuel&gt;=dist){<BR> cout&lt;&lt;count&lt;&lt;endl;<BR> break;<BR> }<BR> fuel += queue.top().fuel;<BR> queue.pop();<BR> count ++;<BR> }<BR>}<BR>