// IO library
#include <cstdio>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>
#include <random>

// contancer library
#include <bitset>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <vector>

using namespace std;

using ll = long long;
using ld = long double;

template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> p);

template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
    os << "[";
    for (auto vv : v) os << vv << ",";
    return os << "]";
}

template <class T>
ostream& operator<<(ostream& os, set<T> v) {
    os << "{";
    for (auto vv : v) os << vv << ",";
    return os << "}";
}

template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> p) {
    return os << "(" << p.first << "," << p.second << ")";
}

template <class K, class T>
ostream& operator<<(ostream& os, map<K, T> v) {
    os << "{";
    for (auto vv : v) os << vv << ",";
    return os << "}";
}

template <class T>
ostream& operator<<(ostream& os, queue<T> q) {
    os << "[";
    while (!q.empty()) {
        os << q.front() << ",";
        q.pop();
    }
    return os << "]";
}

template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q) {
    os << "{";
    while (!q.empty()) {
        os << q.top() << ",";
        q.pop();
    }
    return os << "}";
}

const ll MOD = 1000000007;
// const ll MOD = 998244353;
const int INF = 1 << 25;
// const ll INF = 1LL << 50;
// const ld PI = acos(-1);
// const ld EPS = 1e-10;
// mt19937 mt(ll(time(0)));

template <class T>
vector<T> Vec(size_t l, T v) { return vector<T>(l, v); }

template <class T, class... Ts>
auto Vec(size_t l, Ts... ts) {
    return vector<decltype(Vec<T>(ts...))>(l, Vec<T>(ts...));
}

template <typename T>
inline T sq(T a) { return a * a; }

template <typename T>
inline T iceil(T n, T d) { return (n + d - 1) / d; }

template <typename T>
T gcd(T a, T b) {
    while (b > 0) {
        a %= b;
        swap(a, b);
    }
    return a;
}

template <typename T, typename U>
T ipow(T b, U n) {
    T ret = 1;
    while (n > 0) {
        if (n & 1) ret *= b;
        n >>= 1;
        b *= b;
    }
    return ret;
}

template <typename T, typename U>
T mpow(T b, U n) {
    T ret = 1;
    while (n > 0) {
        if (n & 1) ret = ret * b % MOD;
        n >>= 1;
        b = b * b % MOD;
    }
    return ret;
}

int main() {
    int N;
    cin >> N;

    vector<int> A(N), B(N);
    for (int i = 0; i < N; ++i) {
        cin >> A[i] >> B[i];
    }

    vector<bool> choosed(N, false);
    for (int t = 0; t < N - N / 3; ++t) {
        vector<pair<int, int>> val(N);
        for (int i = 0; i < N; ++i) {
            val[i].second = i;
            val[i].first = (choosed[i] ? INF : A[i] + B[i] * t);
        }

        sort(val.begin(), val.end());
        choosed[val.front().second] = true;
    }

    vector<pair<int, int>> buy;
    for (int i = 0; i < N; ++i) {
        if (!choosed[i]) continue;
        buy.push_back(make_pair(B[i], A[i]));
    }
    sort(buy.rbegin(), buy.rend());

    int ans = 0;
    for (int d = 0; d < buy.size(); ++d) {
        ans += buy[d].second + buy[d].first * d;
    }
    cout << ans << endl;
    return 0;
}