#include<bits/stdc++.h>
#define int long long 
using namespace std;
int n,ans,t=1;
struct bwl{
    int d,l;
};
bwl a[1010];
bool cmp(bwl x,bwl y){
    if(x.d!=y.d) return x.d<y.d;
    else return x.l>y.l;
}
signed main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i].d>>a[i].l;
    }
    sort(a+1,a+1+n,cmp);
    ans+=a[1].l;
    for(int i=1;i<=n;i++){
        if(a[i].d==a[i+1].d) t++;
        else if(a[i].d!=a[i+1].d&&t<=a[i+1].d) ans+=a[i+1].l;
    }
    cout<<ans;
    return 0;
}