#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
struct mem
{
    int x,y;
};
mem v[10005];
bool cmp(mem a, mem b)
{
    if(a.x==b.x) return a.y<b.y;
    return a.x>b.x;
}
int timp[10005];
bool pus[10005];
vector<mem>ans;
int main()
{
    freopen("credite.in","r",stdin);
    freopen("credite.out","w",stdout);
    int s=0,n,y1,x1,cnt=0;
    scanf("%d",&n);
    for(register int i=1;i<=n;i++)
    {
        scanf("%d%d",&x1,&y1);
        v[i].x=x1;
        v[i].y=y1;
    }
    sort(v+1,v+n+1,cmp);
    mem temp;
    for(register int i=1;i<=n;i++)
    {
        if(timp[v[i].y]<v[i].y)
        {

            timp[v[i].y]++;
            temp.x=v[i].x;
            temp.y=v[i].y;
            ans.push_back(temp);
            //if(ans.size()==cnt) break;
        }
    }
    for(register int i=0;i<ans.size();i++)
    {
        int cnt=ans[i].y;
        while(pus[cnt])
            cnt--;
        if(cnt>=1)
        {
            pus[cnt]=1;
            //printf("%d\n",ans[i].x);
            s+=ans[i].x;
        }
    }
    printf("%d",s);
    return 0;
}