#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <cstdlib>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional> 
#include <iomanip>
#include <unordered_map>
#include <memory.h>
#include <unordered_set>
#include <fstream>
#include <random>

using namespace std;

bool cmp(pair<long long int, long long int> a, pair<long long int, long long int> b)
{
	if (a.first == b.first)
	{
		return a.second < b.second;
	}
	return a.first < b.first;
}
int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	int n;
	long long int a, b;
	vector <pair<long long int, long long int>> v;

	cin >> n;

	for (int i = 0; i < n; i++)
	{
		cin >> a >> b;
		v.push_back(make_pair(a, b));
	}
	
	sort(v.begin(), v.end(), cmp);

	long long int res = 0;
	int m = (n - 1) / 2;
	for (int i = 0; i < n - m; i++)
	{
		res += (v[i].first + (i * v[i].second));
		//cout << v[i].first << ' ' << v[i].second << ' ' << (v[i].first + (i * v[i].second)) << '\n';
	}

	cout << res << '\n';

	return 0;
}