#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;

struct Data {
	ll a, b;
	Data() {}
	Data(ll a, ll b) : a(a), b(b) {}
};

ll solve(Data *arr, int n)
{
	ll ret = 0, pen = 0;
	sort(arr, arr + n, [](const Data& lhs, const Data& rhs) {
		return lhs.a * rhs.b > rhs.a * lhs.b;
	});
	
	for (int i = 0; i < n; ++i)
	{
		pen += arr[i].a;
	}
	
	for (int i = 0; i < n; ++i)
	{
		ret += pen * arr[i].b;
		pen -= arr[i].a;
	}
	
	return ret;
}

int main()
{
	int n;
	Data *arr = nullptr;
	scanf("%d", &n);
	arr = new Data[n];
	
	for (int i = 0; i < n; ++i)
	{
		scanf("%lld%lld", &arr[i].a, &arr[i].b);
	}

	printf("%lld\n", solve(arr, n));
	delete [] arr;
	return 0;
}