#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

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

int n, g, w[5010], p[5010];
int r[5010][10010];

int main()
{
	in >> n >> g;

	for (int i = 1; i <= n; ++i)
	{
		in >> w[i] >> p[i];
	}

	for (int j = 0; j <= n; ++j)
		for (int i = 0; i <= g; ++i)
		{
			r[j][i] = 10011;
		}
		
	for (int i = 1; i <= n; ++i)
	{
		for (int j = 1; j <= g; ++j)
		{
			if (w[i] < j)
				r[i][j] = min(r[i - 1][j], r[i - 1][j - w[i]] + p[i]);
			else
				r[i][j] = min(r[i - 1][j], p[i]);
		}
	}

	if (r[n][g] == 10011)
		out << -1;
	else
		out << r[n][g];

	return 0;
}