#include <iostream>
#include <limits.h>
#include <vector>
#include <algorithm>
#include <unordered_map>
#include <map>
#include <stack>
#include <cmath>
#include <string>
#include <fstream>

#define ll long long

using namespace std;

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

const int inf = 1e8;

int main()
{
	int n, need;
	fin >> n >> need;

	vector<int> putere(n);
	vector<int> cost(n);
	for (int i = 0; i < n; i++)
	{
		fin >> putere[i] >> cost[i];
	}

	// dp[i][j] = costul minim pt a produce j energie cu ultimul element i
	vector<vector<int>> dp(n + 1, vector<int>(need + 1, inf));
	dp[0][0] = 0;

	for (int i = 1; i <= n; i++)
	{
		for (int j = 0; j <= need; j++)
		{
			dp[i][j] = dp[i - 1][j];

			if (j >= putere[i - 1])
			{
				dp[i][j] = min(dp[i][j], dp[i][j - putere[i - 1]] + cost[i - 1]);
			}
			else
			{
				dp[i][j] = min(dp[i][j], cost[i - 1]);
			}
		}
	}

	if (dp[n][need] == inf)
	{
		fout << -1;
	}
	else
	{
		fout << dp[n][need];
	}
}

/*

	3
	8

	2 4
	2 3
	8 9
	  

*/