#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[1010][5050], i, j, eg, cg, cgs, egs,pg;
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;
		if (cg < pg)
			pg = cg;
		for (j = pg; 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[G][i] >= W)
		{
			g << i;
			return 0;
		}
	g << -1;
	return 0;
}