#include<fstream>
using namespace std;
int n,S,sol[5002],Gmax=5002,i,j,G,C;
int main()//7/13/2012; 10:40   trebuie sa obtin o greutate cu cost total minim
{
	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>>G>>C;
		for(j=0;j<=S;j++)
		 if(sol[j]!=-1)
		 {
			if(j+G<=S)
			{
				if(sol[j+G]==-1 || C+sol[j] < sol[j+G])
					sol[j+G]=C+sol[j];
			}
			else if(sol[S]==-1 || C+sol[j]<sol[S])
				sol[S]=C+sol[j];
		}
	}
	g<<sol[S]<<'\n';
	f.close();g.close();
return 0;}