#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define eb emplace_back
#define mk make_pair
#define fi first
#define se second
#define cc(x)   cout << #x << " = " << x << endl
#define ok      cout << "ok" << endl
#define endl '\n'

typedef long long ll;
typedef pair<ll,ll> ii;
const int INF = 0x3f3f3f3f;
const double PI = acos(-1.0);

int main() {
    ios_base::sync_with_stdio(false);

    int n;
    cin >>n;

    vector<ii> v;
    ll amin = -1;

    vector<ll> dans;
    for(int i = 0; i < n; i++) {
        ll a, t; cin >>a >>t;
        v.pb(ii(a, t));
        if(i < n-1) dans.pb(a*t);
    }

    sort(v.begin(), v.end(), [](const ii &a, const ii &b) {
        return a.fi*a.se >= b.fi*b.se;
    });

    ll ans = 0;
    for(int i = 0; i < n; i++) {
        ans += ((n-i-1)*(dans[i]-(v[i].fi*v[i].se)));
        cc(ans);
    }

    cout <<ans <<endl;
    return 0;
}