Problem:
Score : 400 points

Problem Statement

Dolphin is planning to generate a small amount of a certain chemical substance C.

In order to generate the substance C, he must prepare a solution which is a mixture of two substances A and B in the ratio of M_a:M_b.

He does not have any stock of chemicals, however, so he will purchase some chemicals at a local pharmacy.

The pharmacy sells N kinds of chemicals. For each kind of chemical, there is exactly one package of that chemical in stock.

The package of chemical i contains a_i grams of the substance A and b_i grams of the substance B, and is sold for c_i yen (the currency of Japan).

Dolphin will purchase some of these packages. For some reason, he must use all contents of the purchased packages to generate the substance C.

Find the minimum amount of money required to generate the substance C.

If it is not possible to generate the substance C by purchasing any combination of packages at the pharmacy, report that fact.

Constraints

1≦N≦40

1≦a_i,b_i≦10

1≦c_i≦100

1≦M_a,M_b≦10

gcd(M_a,M_b)=1

a_i, b_i, c_i, M_a and M_b are integers.

Input

The input is given from Standard Input in the following format:

N M_a M_b
a_1 b_1 c_1
a_2 b_2 c_2
:
a_N b_N c_N

Output

Print the minimum amount of money required to generate the substance C. If it is not possible to generate the substance C, print -1 instead.

Sample Input 1

3 1 1
1 2 1
2 1 2
3 3 10

Sample Output 1

3

The amount of money spent will be minimized by purchasing the packages of chemicals 1 and 2.

In this case, the mixture of the purchased chemicals will contain 3 grams of the substance A and 3 grams of the substance B, which are in the desired ratio: 3:3=1:1.

The total price of these packages is 3 yen.

Sample Input 2

1 1 10
10 10 10

Sample Output 2

-1

The ratio 1:10 of the two substances A and B cannot be satisfied by purchasing any combination of the packages. Thus, the output should be -1.

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using static MyIO;
using static MyBinarySearch;


public class MedicineSet : IComparable<MedicineSet>
{
	public int Rate { get; private set; } // sum(a) * Mb - sum(b) * Ma
	public int Cost { get; private set; }

	public MedicineSet(int rate, int cost)
	{
		Rate = rate;
		Cost = cost;
	}

	public int CompareTo(MedicineSet x)
	{
		return Rate - x.Rate;
	}
}


public class D
{
	public static void Main()
	{
		int N = GetInt();
		int Ma = GetInt();
		int Mb = GetInt();
		int[] a = new int[N];
		int[] b = new int[N];
		int[] c = new int[N];
		for(int i = 0; i < N; i++)
		{
			a[i] = GetInt();
			b[i] = GetInt();
			c[i] = GetInt();
		}

		int size0 = (N + 1)/2;
		int size1 = N - size0;

		bool exist = false;
		int ans = int.MaxValue;

		List<MedicineSet> sets0 = new List<MedicineSet>(size0);
		for(int s = 1; s < (1 << size0); s++)
		{
			int rate = 0;
			int cost = 0;
			for(int i = 0; i < size0; i++)
			{
				if(((s >> i) & 1) == 0)
					continue;
				rate += a[i] * Mb - b[i] * Ma;
				cost += c[i];
			}
			sets0.Add(new MedicineSet(rate, cost));

			if(rate == 0)
			{
				exist = true;
				ans = Math.Min(ans, cost);
			}
		}

		List<MedicineSet> sets1 = new List<MedicineSet>(size1);
		for(int s = 1; s < (1 << size1); s++)
		{
			int rate = 0;
			int cost = 0;
			for(int i = 0; i < size1; i++)
			{
				if(((s >> i) & 1) == 0)
					continue;
				rate += a[i + size0] * Mb - b[i + size0] * Ma;
				cost += c[i + size0];
			}
			sets1.Add(new MedicineSet(rate, cost));

			if(rate == 0)
			{
				exist = true;
				ans = Math.Min(ans, cost);
			}
		}
		sets1.Sort(
			(x,y) => (x.Rate - y.Rate) != 0 ?
				(x.Rate - y.Rate) : (x.Cost - y.Cost));

		
		foreach(MedicineSet set0 in sets0)
		{
			int index = sets1.LowerBound(new MedicineSet(-set0.Rate, -1));
			if((index < 0) || (index >= sets1.Count))
				continue;
			if(sets1[index].Rate != -set0.Rate)
				continue;
			
			exist = true;
			ans = Math.Min(ans, set0.Cost + sets1[index].Cost);
		}
		Console.WriteLine(exist ? ans : -1);
	}
}


public static class MyBinarySearch
{
	public static int LowerBound<T>(
		this List<T> list, int first, int end, T value, IComparer<T> comparer)
	{
		int low = first;
		int high = end;
		while(low < high)
		{
			int mid = ((high - low) >> 1) + low;
			if(comparer.Compare(list[mid], value) < 0)
				low = mid + 1;
			else
				high = mid;
		}
		return low;
	}

	public static int LowerBound<T>(this List<T> list, T value)
	{
		return list.LowerBound(0, list.Count, value, Comparer<T>.Default);
	}

	public static int UpperBound<T>(
		this List<T> list, int first, int end, T value, IComparer<T> comparer)
	{
		int low = first;
		int high = end;
		while(low < high)
		{
			int mid = ((high - low) >> 1) + low;
			if(comparer.Compare(list[mid], value) <= 0)
				low = mid + 1;
			else
				high = mid;
		}
		return low;
	}

	public static int UpperBound<T>(this List<T> list, T value)
	{
		return list.UpperBound(0, list.Count, value, Comparer<T>.Default);
	}
}


public static class MyIO
{
	private static string[] args = null;
	private static int num = -1;
	private static int used = -1;

	private static string getArg()
	{
		if(used == num)
		{
			args = Console.ReadLine().Split(' ');
			num = args.Length;
			used = 0;
		}
		return args[used++];
	}

	public static int GetInt(){ return int.Parse(getArg()); }
	public static long GetLong(){ return long.Parse(getArg()); }
	public static double GetDouble(){ return double.Parse(getArg()); }
	public static string GetString(){ return getArg(); }
}