#include<iostream>

#include<cstdio>

#include<cmath>

#include<algorithm>

#include<cstring>

#include<cstdlib>

using namespace std;

#define N 11000

#define INF 0xfffffff

struct node

{

    int a,b;

}p[N];

int cmp(node a, node b)

{

	return a.a > b.a;

}

int main()

{

    int n,i,j,vis[N];

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

    {

        memset(vis,0,sizeof(vis));

        memset(p,0,sizeof(p));

        for(i=0;i<n;i++)

        scanf("%d %d",&p[i].a,&p[i].b);

        sort(p,p+n,cmp);

        int sum=0;

        for(i=0;i<n;i++)

        {

            for(j=p[i].b;j>0;j--)

            {

                if(vis[j]==0)

                {

                    sum=sum+p[i].a;

                    vis[j]=1;

                    break;

                }

            }

        }

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

    }

    return 0;

}