#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
struct pr
{
    int x,y;
} v[10005];
bool comp(pr a, pr b)
{
    return (a.x>b.x);
}
int n,i,frec[10005],nr,s,maxx,p,j;
ifstream cin("credite.in");
ofstream cout("credite.out");
void citiren()
{
    cin>>n;
}
void citire()
{
    for(i=1; i<=n; i++){
        cin>>v[i].x>>v[i].y;
        maxx=max(maxx,v[i].y);
    }
    sort(v+1,v+n+1,comp);
}
void rezolvare()
{
    for(i=1;i<=n;i++)
    {
        p=-1;
        for(j=1;j<=v[i].y;j++)
            if(frec[j]==0)
                p=j;
        frec[p]=v[i].x;
    }
    for(i=1;i<=maxx;i++)
        s=s+frec[i];
}
void printare()
{
    cout<<s;
}
int main()
{
    citiren();
    citire();
    rezolvare();
    printare();
    return 0;
}