#include <fstream>

using namespace std;

const char InFile[]="energii.in";
const char OutFile[]="energii.out";
const int MaxN=5005;
const int MAX=1<<30;

ifstream fin(InFile);
ofstream fout(OutFile);

int W,CGi,EGi,G,sol,cost[MaxN];

int main()
{
	for(register int i=0;i<MaxN;++i)
	{
		cost[i]=MAX;
	}
	fin>>G>>W;
	cost[0]=1;
	for(register int i=0;i<G;++i)
	{
		fin>>EGi>>CGi;
		for(register int j=MaxN-1;j>=0;--j)
		{
			if(cost[j]!=MAX)
			{
				int pos=j+EGi;
				if(pos>W)
				{
					pos=W;
				}
				cost[pos]=min(cost[pos],cost[j]+CGi);
			}
		}
	}
	fin.close();

	if(cost[W]==MAX)
	{
		cost[W]=0;
	}
	fout<<cost[W]-1;
	fout.close();
	return 0;
}