#include <algorithm>
#include <iostream>
#include <utility>
using namespace std;
constexpr int N = 114514;
int n;
pair<int, int> nums[N];
int dad[N];
int res;
int find (int now) {
if (now == dad[now]) {
return now;
}
return dad[now] = find (dad[now]);
}
int main () {
while (cin >> n) {
for (int i = 1; i <= n; i++) {
cin >> nums[i].first >> nums[i].second;
}
sort (nums + 1, nums + 1 + n);
for (int i = 1; i <= 10000; i++) {
dad[i] = i;
}
res = 0;
for (int i = n; i >= 1; i--) {
int t = find (nums[i].second);
if (t) {
res += nums[i].first;
dad[t] = t - 1;
}
}
cout << res << endl;
}
return 0;
}