#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    
    int n;cin>>n;
    int k=n/3;
    vector<pair<ll,ll>> v(n);
    rep(i,n) cin>>v[i].first>>v[i].second;

    sort(ALL(v),[](pair<ll,ll> a,pair<ll,ll> b){
        return a.second>b.second;
    });

    vector<vector<ll>> dp(n+1,vector<ll>(k+1,LINF));
    dp[0][0]=0;
    
    rep(i,n){
        rep(j,k+1){
            // 買う．i-j日目
            chmin(dp[i+1][j],dp[i][j]+v[i].first+v[i].second*(0ll+i-j));
            // 買わない
            if(j<k) chmin(dp[i+1][j+1],dp[i][j]);
        }
    }
    cout<<dp[n][k]<<endl;
    return 0;
}