#include <fstream>

#define MAX_N ((const unsigned int)1001)
#define MAX_G ((const unsigned int)5001)
#define MAX_E ((const unsigned int)10001)
#define INFINITE ((const unsigned int)-1)

int N, W;
int sol = INFINITE;

class Generator
{
public:
	int energie;
	int cost;
}generator[MAX_N];

int cost[MAX_E];

int main()
{
	std::ifstream fin("energii.in");
	std::ofstream fout("energii.out");

	fin>>N>>W;

	for (int i = 0; i < N; ++ i)
		fin>>generator[i].energie>>generator[i].cost;

	for (int i = 0; i < N; ++ i)
	{
		for (int j = W; j >= 0; j --)
		{
			if (cost[j + generator[i].energie] < cost[j] + generator[i].cost)
			{
				cost[j + generator[i].energie] = cost[j] + generator[i].cost;

				if (sol < cost[j] + generator[i].cost)
					sol = cost[j] + generator[i].cost;
			}
		}
	}

	if (sol == INFINITE)
		sol = -1;

	fout<<sol;

	fin.close();
	fout.close();

	return 0;
}