#include<fstream>
using namespace std;
ofstream out("rucsac.out");
int n,gmax,c[10001],g[10001],Cmax[10001],uz[1000][1000];
void citire();
void dinamic();
int main()
{
	citire();
	dinamic();
	if(Cmax[gmax]==-1)
		out<<-1;
	else
		
	out<<Cmax[gmax];
	return 0;
}
void citire()
{
	ifstream in("rucsac.in");
	int i;
	in>>n>>gmax;
	for(i=1;i<=n;i++)
		in>>g[i]>>c[i];
}
void dinamic()
{
	int S,k,i;
	for(S=1;S<=gmax;S++)
		Cmax[S]=-1;
	for(S=1;S<=gmax;S++)
		for(i=1;i<=n;i++)
			if(g[i]<=S&&Cmax[S-g[i]]!=-1&&uz[S-g[i]][i]==0)
				if(Cmax[S]<c[i]+Cmax[S-g[i]])
				{
					
					Cmax[S]=c[i]+Cmax[S-g[i]];
						for(k=1;k<=n;k++)
							uz[S][k]=uz[S-g[i]][k];
						uz[S][i]=1;
				}
}