#include "bits/stdc++.h"
using namespace std;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define rrep(i,n) for( int i = n; i >= 0; i-- )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define RREP(i,s,t) for( int i = s; i >= t; i-- )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000
#define int long long

int dp[2010][2010];// dp[i][j]:= i個目までの商品からj個買った時の最少額

signed main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N; cin >> N;
    pair<int, int> P[100010];
    rep(i, N) cin >> P[i].second >> P[i].first;
    sort(P, P + N, greater<pair<int, int>>());
    rep(i, 2010) rep(j, 2010) dp[i][j] = INF2;
    dp[0][0] = 0;
    rep(i, N) {
        rep(j, N) {
            dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j] + P[i].second + P[i].first * j);
            dp[i + 1][j] = min(dp[i + 1][j], dp[i][j]);
        }
    }
    cout << dp[N][(N*2+2)/3] << endl; 



    return 0;
}