# define _CRT_SECURE_NO_WARNINGS 1
# include <iostream>
# include <numeric>
# include <string>
# include <bitset>
# include <vector>
# include <algorithm>
# include <cstdlib>
# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iomanip>
# include <queue>
# include <sstream>
# include <climits>
# include <cmath>
# include <list>
# include <functional>
# include <string>
# include <ctime>
# include <set>
# include <forward_list>
# include <map>
# include <stack>
using namespace std;

# define INF ((int)(1<<25))
# define REP(i,n) for(int i=0;i<(int)n;i++)
# define FOR(i,n) REP(i,n)
# define TORAD 2.0*M_PI/360.0
# define INT(x) int x;cin>>x;
# define ALL(x) (x).begin(),(x).end()
# define RALL(x) (x).rbegin(),(x).rend()
# define DEBUG(x) cout<<#x<<" :"<<x<<endl;
# define EPS 1e-12



template<class T> void debug(T a) { for (auto i : a)cout << i << endl; }

typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef pair<int, pii> piii;
int dx[4] = { 0,1,0,-1 }, dy[4] = { -1,0,1,0 };

int n;
vector<pii> a;

int hoge(int t,int d,vi &v)
{
	if (accumulate(ALL(v),0) == n)return 0;
	int ans = INT_MAX;
	for (int i = 0; i < n; i++)
	{
		if (v[i])continue;
		v[i] = 1;
		ans = min(ans, hoge(t, a[i].second,v) + t*d*a[i].first*a[i].second);
		v[i] = 0;
	}
	return ans;
}

int main()
{
	
	cin >> n;
	FOR(i, n)
	{
		pii p; cin >> p.first >> p.second;
		a.push_back(p);
	}
	vi v(n, 0); int ans = INT_MAX;
	FOR(i, n)
	{
		v[i] = 1;
		ans = min(ans, hoge(a[i].first, a[i].second, v));
		v[i] = 0;
	}
	cout << ans << endl;

}