#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <climits>
#include <cstring>

#define rep(i, m, n) for(int i=int(m);i<int(n);i++)
#define all(c) begin(c),end(c)

template<typename T1, typename T2>
inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }

template<typename T1, typename T2>
inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }

//改造
typedef long long int ll;
using namespace std;
#define INF (1 << 30) - 1
#define INFl (ll)5e15
#define DEBUG 0 //デバッグする時1にしてね
#define dump(x)  cerr << #x << " = " << (x) << endl
#define MOD 1000000007


//ここから編集する
class Solve {
public:
    void input() {

    }

    void solve() {
        input();
        int N;
        cin >> N;
        int final = N - (N / 3);
        using P = pair<ll, ll>;
        vector<P> vp(N);
        rep(i, 0, N) {
            cin >> vp[i].first >> vp[i].second;
        }

        sort(all(vp), [&](P a, P b) {
            return a.first + a.second * final < b.first + b.second * final;
        });

        vector<P> items;
        for (int i = 0; i < final; ++i) {
            items.push_back(vp[i]);
        }

        sort(all(items), [](P a, P b) {
            return a.second > b.second;
        });

        ll ans = 0ll;
        for (int i = 0; i < final; ++i) {
            ll tmp = items[i].first + items[i].second * i;
            ans += tmp;
        }
        cout << ans << endl;


    }
};


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    Solve().solve();


    return 0;
}