#include <string.h>

 #include <iostream>

 #include <queue>

 #include <stdio.h>

 using namespace std;

 struct product{

     int deadline;

     int val;

     friend bool operator<(product n1,product n2)

     {

         return n1.val<n2.val;

     }

 }q;

 bool mark[];

 int main()

 {

    // freopen("in.txt","r",stdin);

     priority_queue<product> s;

     int m;

     while(scanf("%d",&m)!=EOF)

     {

         for(int i=;i<m;i++)

         {

             scanf("%d%d",&q.val,&q.deadline);

             s.push(q);

         }

         memset(mark,true,sizeof(mark));

         int ans=;

         while(!s.empty())

         {

             q=s.top();

             s.pop();

             for(int i=q.deadline;i>=;i--)

             {

                 if(mark[i]) {

                     ans+=q.val;

                     mark[i]=false;

                     break;

                 }

             }

         }

         printf("%d\n",ans);

     }

     return ;

 }