#include <iostream>
#include <bitset>
#include <vector>
#include <queue>
#include <algorithm>
#include <map>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<pair<int,int>> vec;
    vec.reserve(n);
    int maxx = 0;
    for(int i =0 ;i  < n; ++i){
        int time, value;
        cin >> time >> value;
        maxx = max(time,maxx);
        vec.push_back({time,value});
    }
    sort(vec.begin(),vec.end(),[&](const pair<int,int>& a, const pair<int,int>& b){
        if (a.first == b.first){
            return a.second > b.second;
        }else{
            return a.first < b.first;
        }
    });
    long long ans = 0;
    vector<int> ansv(maxx+1,0);
    for(int i = 1 ; i <= maxx; ++i){
        auto it = lower_bound(vec.begin(),vec.end(),i,[&](const pair<int,int>& a, int b){
            return a.first < b;
        });
        if(it != vec.end()) {
            ansv[i] =it->second;
            vec.erase(it);
        }
    }
    for(int i = 0; i < vec.size(); ++i){
        int l = 1, r = vec[i].first;
        int minn_index = -1, minn = 1000000000;
        for(;l < r+1; ++l){
            if(ansv[l] < minn){
                minn = ansv[l];
                minn_index =l;
            }
        }
        if(minn < vec[i].second){
            ansv[minn_index] = vec[i].second;
        }
    }
    for(auto it: ansv){
        ans += it;
    }
    cout << ans << '\n';
    return 0;
}