# include <stdio.h>
# include <algorithm>
# include <string.h>
using namespace std;
int fa[10010];
struct node
{
	int p;
	int d;
};
struct node a[10010];
bool cmp(node a1,node a2)//利润从大到小
{
	return a1.p>a2.p;
}
int find(int x)
{
	if(fa[x]==-1)
		return x;
	return fa[x]=find(fa[x]);
}
int main()
{
	int i,n,sum;
	while(~scanf("%d",&n))
	{
        memset(fa,-1,sizeof(fa));
		for(i=0;i<n;i++)
			scanf("%d%d",&a[i].p,&a[i].d);
		sort(a,a+n,cmp);
		sum=0;
		for(i=0;i<n;i++)
		{
			int x=find(a[i].d);
			if(x>0)
			{
				fa[x]=x-1;
				sum+=a[i].p;
			}
		}
		printf("%d\n",sum);
	}
	return 0;
}