#include<fstream>
#include<bitset>
#include<vector>
using namespace std;
#define nm 5001
#define min(x,y) ((x)<(y)?(x):(y))
ifstream f("energii.in");
ofstream g("energii.out");
vector<int>e,ct;
int map[1002][nm+1];
int n,ec,min1,i,j;
int main()
{	f>>n>>ec;
	e.resize(n+2,0);
	ct.resize(n+2,0);
	for(i=1;i<=n;i++)
		f>>e[i]>>ct[i];
	for(j=1;j<=ec;j++)
		map[0][j]=500000;
	min1=500000;
	for(i=1;i<=n;i++)
		for(j=1;j<=nm;j++)
		{	if(map[i-1][j]!=0)
				map[i][j]=min(map[i-1][j],map[i-1][j-e[i]]+ct[i]);
			else
				if(j-e[i]>=0 && map[i-1][j-e[i]]!=0)
					map[i][j]=map[i-1][j-e[i]]+ct[i];
		}
	for(i=1;i<=n;i++)
		for(j=ec;j<=ec+50;j++)
			if(min1>map[i][j]&&map[i][j]!=0&&map[i][j]!=500000)
				min1=map[i][j];
	if(min1!=500000)
		g<<min1;
	else g<<-1;
	f.close();
	g.close();
	return 0;
}