#include <fstream>
#include <limits.h>
#include <algorithm>
using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");

const int WMAX = 5001;
const int MAX = 10005;
int optim[2 * WMAX];
int e, c, n, g, w;

int main()
{
	fin >> g >> w;
	for (int i = 1; i <= 2 * w; ++i)
		optim[i] = MAX;
	while (g--)
	{
		fin >> e >> c;
		for (int i = 2 * w - e; i >= 0; --i)
			optim[i + e] = min(optim[i + e], optim[i] + c);
	}
	int sol = MAX;
	for (int i = w; i <= 2 * w; ++i)
		sol = min(sol, optim[i]);
	if (sol == MAX) sol = -1;
	fout << sol << "\n";
	return 0;
}