#include <bits/stdc++.h>
typedef long long ll;
#define rep(i,m,n) for(ll i = (m); i < (n); i++)
#define rrep(i,m,n) for(ll i = (m); i >= (n); i--)
#define print(x) cout << (x) << endl;
#define print2(x,y) cout << (x) << " " << (y) << endl;
#define printa(x,n) for(ll i = 0; i < n; i++){ cout << (x[i]) << " \n"[i == n-1];}
#define printp(x,n) for(ll i = 0; i < n; i++){ cout << "(" << x[i].first << ", " << x[i].second << ") "; } cout << endl;
#define INF (1e18 + 7)
using namespace std;
const ll MOD = 1e9 + 7;
typedef pair<ll, ll> lpair;
struct Combination{
private:
    ll N;
    vector<ll> fac, facinv;

public:
    Combination(ll n){
        N = n;
        fac.push_back(1); fac.push_back(1);
        rep(i,2,N+1) fac.push_back(fac[i-1] * i % MOD);
        rep(i,0,N+1) facinv.push_back(power(fac[i], MOD-2));
    }
    ll power(ll x, ll n){
        if(n == 0) return 1LL;
        ll res = power(x * x % MOD, n/2);
        if(n % 2 == 1) res = res * x % MOD;
        return res;
    }
    ll nck(ll n, ll k){
        if(k == 0 || n == k) return 1LL;
        return fac[n] * facinv[k] % MOD * facinv[n-k] % MOD;
    }
    ll npk(ll n, ll k){
        if(k == 0 || n == k) return 1LL;
        return fac[n] * facinv[n-k] % MOD;
    }
    ll get(ll x){return fac[x];};
    ll getinv(ll x){return facinv[x];};
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll N;
    ll A[2010], B[2010];
    cin >> N;
    rep(i,0,N) cin >> A[i] >> B[i];
    vector<lpair> lp;
    rep(i,0,N) lp.push_back(make_pair(B[i], A[i]));
    sort(lp.begin(), lp.end(), greater<lpair>());
    ll ans = INF;
    ll days = 0;
    days += 2 * N/3;
    ll tada = N/3;
    days += N % 3;
    rep(i,0,N){
        ll tt = 0;
        tt += lp[i].second;
        ll cnt = 0;
        ll idx = 1;
        rep(j,0,N){
            if(cnt < tada && j != i){
                cnt++;
            }else if(j != i){
                tt += lp[j].second + lp[j].first * idx;
                idx++;
            }
        }
        // print(tt);
        ans = min(ans, tt);
    }
    print(ans);

    


 }