#include<iostream>
#include <vector>
#include<algorithm>
using namespace std;
const int N = 10010;
int fa[N];
int n;

typedef pair<int, int> PII;

void init() {
    for(int i = 0; i < N; i++) fa[i] = i;
}

int find(int x) {
    return fa[x] == x ? x : fa[x] = find(fa[x]);
}

void merge(int x, int y) {
    fa[find(x)] = find(y);
}

bool cmp(PII a, PII b) {
    return a.first > b.first;
}

int main() {
    while(cin >> n) {
        int ans = 0;
        vector<PII> pros(n);
        for(int i = 0; i < n; i++) cin >> pros[i].first >> pros[i].second;
        init();

        sort(pros.begin(), pros.end(), cmp);

        for(int i = 0; i < n; i++) {
            int x = find(pros[i].second);
            if(x) {
                ans += pros[i].first;
                merge(x, x-1);
            }
        }
        cout << ans << endl;
    }
    return 0;
}