#include <fstream>
using namespace std;

ifstream f ("energii.in");
ofstream g ("energii.out");

int main()
{
	int n, t, p[3][1005];

	f>>n>>t;
	for (int i=1; i<=n; ++i)
	{
		f>>p[1][i];
		f>>p[2][i];
	}

	for (int i=1; i<n; ++i)
		for (int j=i+1; j<=n; ++j)
			if (((float)p[1][i]/p[2][i])<((float)p[1][j]/p[2][j]))
			{
				int aux=p[2][i];
				p[2][i]=p[2][j];
				p[2][j]=aux;
				aux=p[1][i];
				p[1][i]=p[1][j];
				p[1][j]=aux;
			}
	
	int s1=0,s2=0;
	for (int i=1; i<=n; ++i)
	{
		s1+=p[1][i]; s2+=p[2][i];
		if (s1>=t) {g<<s2; i=n+1;}
		else if (i==n) g<<-1;
	}
	return 0;
}