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

using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    auto solve = [&]() {
        int n;
        cin >> n;

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

        int sa = 0, sb = 0;
        i64 ans = 0;

        for (int i = n - 1; i >= 0; i--) {
            ans += max(1LL * a[i] * sb, 1LL * b[i] * sa);
            sb += b[i];
            sa += a[i];
        }

        cout << ans << '\n';
    };
    
    solve();
    
    return 0;
}