#include<fstream>
#include<string.h>
#include<ctype.h>
#include<iostream>
#include<algorithm>
#include<map>
#include<unordered_map>
#include<array>
#include<deque>
#include<unordered_set>
#include<set>
#include<math.h>
using namespace std;
int G, W, dp[5050],i,j,eg,cg,cgs,egs;
vector<pair<int, int>>v[1010];
vector<pair<int, int>>::iterator it;
int main()
{
	ifstream f("energii.in");
	ofstream g("energii.out");
	f >> G;
	f >> W;
	for (i = 1; i <= G; i++)
	{
		f >> eg >> cg;
		cgs += cg;
		v[i].push_back(make_pair(cg, eg));
	}
	sort(v + 1, v + G + 1);
	it = v[1].begin();
	dp[it->first] = it->second;
	for (j = it->first+1; j <= cgs; j++)
	{
		dp[j] = dp[j - 1];
		for (i = 1; i <= G; i++)
			if (j >= v[i].begin()->first)
			{
				if (j - v[i].begin()->first != v[i].begin()->first)
					dp[j] = max(dp[j], dp[j - v[i].begin()->first] + v[i].begin()->second);
			}
	}
	/*
	cgs += cg;
		for (j = 1; j <= cgs; j++)
		{
			dp[i][j] = max(dp[i][j-1],dp[i-1][j]);
			if (j >= cg)
				dp[i][j] = max(dp[i][j], dp[i-1][j - cg] + eg);
		}
	*/
	for(i=0;i<=cgs;i++)
		if (dp[i]>= W)
		{
			g << i;
			return 0;
		}
	g << -1;
	return 0;
}