#include<iostream>
#include<vector>
#include<algorithm>
#include<functional>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<unordered_map>
#include<climits>
#include<cstdlib>
#include<cmath>
#include<string>
#include<iomanip>
#include<bitset>

using namespace std;

#define ll long long int

ll const MOD = 1000000007;
ll const INF = (long long int)1 << 61;

ll mypow(ll x,ll n){
    ll ret = 1;
    while(n > 0){
        if(n&1){
            ret = (ret*x)%MOD;
        }
        x = (x*x)%MOD;
        n >>= 1;
    }
    return ret;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    ll n;
    cin >> n;

    vector<ll> a(n),b(n);

    for(int i = 0; i < n; i++){
        cin >> a[i] >> b[i];
    }

    vector<ll> t;
    ll z = 0;
    bool flag = true;
    for(int i = 1; i <= n; i++){
        if(i % 3 == 0){
            t.push_back(i/3 +  (i/3 - 1)*2);
        }
    }

    vector<bool> used(n,false);
    for(int i = 0; i < t.size(); i++){
        ll m = 0;
        ll midx = 0;
        for(int j = 0; j < n; j++){
            if(!used[j]){
                if(a[j] + t[i]*b[j] > m){
                    m = a[j] + t[i]*b[j];
                    midx = j;
                }
            }
        }
        used[midx] = true;
    }

    vector<pair<ll,ll>> s;
    for(int i = 0; i < n; i++){
        if(!used[i]){
            s.push_back(make_pair(b[i],a[i]));
        }
    }

    sort(s.begin(),s.end(),greater<pair<ll,ll>>());

    ll ans = 0;
    for(int i = 0; i < s.size(); i++){
        ans += s[i].first*i + s[i].second;
    }

    cout << ans << endl;

    return 0;
}