#include <fstream>
#include <algorithm>
using namespace std;
struct Probl{
int T;
int C;
bool seFace = false;
};
bool cmp(Probl a, Probl b){
if(a.C == b.C)
return a.T < b.T;
else return a.C > b.C;
}
Probl vec[10001];
bool timp[100000];
int main(){
ifstream fin("credite.in");
ofstream fout("credite.out");
int n;
fin >> n;
for(int i = 0; i < n; i++){
fin >> vec[i].C >> vec[i].T;
}
fin.close();
sort(vec, vec+n, cmp);
int total = 0;
for(int i = 0; i < n; i++){
int t = vec[i].T;
if(!timp[t]){
timp[t] = true;
vec[i].seFace = true;
}else{
int j;
for(j = t-1; j>0; j--){
if(!timp[j])
break;
}
if(j != 0){
timp[j] = true;
vec[i].seFace = true;
}
}
}
for(int i = 0; i < n; i++)
if(vec[i].seFace)
total += vec[i].C;
fout << total;
fout.close();
}
