#include <bits/stdc++.h>

using namespace std;

using int64 = long long;
const int mod = 1e9 + 7;
const int inf = (1 << 30) - 1;
const int64 infll = (1LL << 61) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}


template< typename T >
struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WeightedGraph = vector< Edges< T > >;
using UnWeightedGraph = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;


template< typename T >
T hungarian(Matrix< T > &A) {
  const T infty = numeric_limits< T >::max();
  const int N = (int) A.size();
  const int M = (int) A[0].size();
  vector< int > P(M), way(M);
  vector< T > U(N, 0), V(M, 0), minV;
  vector< bool > used;

  for(int i = 1; i < N; i++) {
    P[0] = i;
    minV.assign(M, infty);
    used.assign(M, false);
    int j0 = 0;
    while(P[j0] != 0) {
      int i0 = P[j0], j1 = 0;
      used[j0] = true;
      T delta = infty;
      for(int j = 1; j < M; j++) {
        if(used[j]) continue;
        T curr = A[i0][j] - U[i0] - V[j];
        if(curr < minV[j]) minV[j] = curr, way[j] = j0;
        if(minV[j] < delta) delta = minV[j], j1 = j;
      }
      for(int j = 0; j < M; j++) {
        if(used[j]) U[P[j]] += delta, V[j] -= delta;
        else minV[j] -= delta;
      }
      j0 = j1;
    }
    do {
      P[j0] = P[way[j0]];
      j0 = way[j0];
    } while(j0 != 0);
  }
  return -V[0];
}

int main() {
  int N;
  cin >> N;
  deque< pair< int64, int64 > > A(N);

  int free = 0, d = 0;
  for(int i = 0; i < N; i++) {
    cin >> A[i].first >> A[i].second;
    if(i % 3 == 2) ++free;
    else ++d;
  }

  Matrix< int64 > mat(N + 1, vector< int64 >(N + 1));
  for(int i = 0; i < N; i++) {
    for(int j = 0; j < N; j++) {
      mat[i + 1][j + 1] = i < d ? A[j].first + A[j].second * i : 0;
    }
  }
  cout << hungarian(mat) << endl;
}