#include <bits/stdc++.h>
using namespace std;
int main () {
	int N;
	cin >> N;
	std::vector<int> A(N), B(N), C(N);
	iota(C.begin(), C.end(), 0);
	for (int i = 0; i < N; i ++) {
		cin >> A[i] >> B[i];
	}
	sort(C.begin(), C.end(), [&](int i, int j) {return A[j] * B[i] > A[i] * B[j];});
	long long ans = 0, sum = 0;
	for (auto i : C) {
		ans += sum * A[i];
		sum += B[i];
	}
	cout << ans << endl;
}