#include<fstream>
#define inf 2000000000
using namespace std;
int n,s,sol[5002],i,j,minn,poz,G,C;
int main()
{
	ifstream f("energii.in");ofstream g("energii.out");
	f>>n>>s;
	for(i=1;i<=s;i++)sol[i]=inf;
	for(i=1;i<=n;i++)
	{
	 f>>G>>C;
	  for(j=1;j<=s;j++)
	   if(j>=G && sol[j-G]+C<sol[j] && sol[j-G]!=inf )sol[j]=sol[j-G]+C;
	}
	if(sol[s]==inf)g<<"-1";else
	g<<sol[s]<<'\n';
	f.close();g.close();
return 0;}