#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using ll =  long long ;
using P = pair<int,int> ;
const int INF = 1e9;
const int MOD = 1000000007;

int main(){
    int n;
    cin >> n;
    vector<P> ab(n);
    rep(i,n) cin >> ab[i].second >> ab[i].first;
    sort(ab.begin(),ab.end(),greater<P>());
    vector<vector<int>> dp(n+1,vector<int>(n+1,INF));
    dp[0][0] = 0;
    for(int i=1;i<=n;i++){
        for(int j=0;j<=n;j++){
            if(j>0) dp[i][j] = min(dp[i-1][j-1], dp[i-1][j] + ab[i-1].second + ab[i-1].first*(i-j-1));
            else dp[i][j] = dp[i-1][j] + ab[i-1].second + ab[i-1].first*(i-j-1);
        }
    }
    cout << dp[n][n/3] << endl;
    return 0;
}