#include<fstream>
#define min(a,b) (a<b)?a:b
using namespace std;
int sol[5002],n,s;
int i,j,e,c;
int main()
{
	ifstream f("energii.in");ofstream g("energii.out");
	f>>n>>s;
	for(i = 1; i <=s; i++)
		sol[i]=-1;
	for(i=1;i<=n;i++)
	{
		f>>e>>c;
		for(j=0;j<=s;j++)
		 if(sol[j]!=-1 && (sol[j+e]==-1 || sol[j]+c<sol[j+e] ) )
		    sol[j+e]=c+sol[j];
	}
	g<<sol[s];
	f.close();g.close();
	return 0;
}