#include <bits/stdc++.h>
#define ft first
#define sc second
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define pt(sth) cout << sth << "\n"
#define chmax(a, b) {if(a<b) a=b;}
#define chmin(a, b) {if(a>b) a=b;}
#define moC(a, s, b) (a)=((a)s(b)+MOD)%MOD
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
static const ll INF=1e18;
static const ll MAX=1e5+7;
static const ll MOD=1e9+7;


ll dp[2020][2020];

int main(void) {
  ll N;
  cin >> N;
  ll i, j;
  P itm[2020];
  
  for(i=0; i<N; i++) {
    cin >> itm[i].sc >> itm[i].ft;
  }
  sort(itm, itm+N);
  reverse(itm, itm+N);
  
  for(i=0; i<2020; i++) {
    for(j=0; j<2020; j++) {
      dp[i][j]=INF;
    }
  }
  dp[0][0]=0;
  
  for(i=0; i<N; i++) {
    for(j=0; j<=N/3; j++) {
      chmin(dp[i+1][j], dp[i][j]+itm[i].sc+itm[i].ft*(i-j));
      chmin(dp[i+1][j+1], dp[i][j]);
    }
  }
  
  pt(dp[N][N/3]);
}