#include<fstream.h>
long long s2,g,w,e[1002],c[1002],i,z,s;
float r[1001];
int main()
{
ifstream in("energii.in");
ofstream out("energii.out");
in>>g>>w;
for(i=1;i<=g;i++)
	{
	in>>e[i]>>c[i];
	r[i]=(float)e[i]/c[i];
	}
for(i=1;i<=g;i++)
	if(r[i]<r[i-1])
		while(r[i]<r[i-1])
			{
			z=r[i];
			r[i]=r[i-1];
			r[i-1]=z;

			z=c[i];
			c[i]=c[i-1];
			c[i-1]=z;

			z=e[i-1];
			e[i-1]=e[i];
			e[i]=z;
			}
/*for(i=1;i<=g;i++)
	out<<e[i]<<" ";
	out<<"\n";
for(i=1;i<=g;i++)
	out<<c[i]<<" ";
	out<<"\n";
for(i=1;i<=g;i++)
	out<<r[i]<<" ";
	out<<"\n";
	*/
for(i=g;i!=0 && s<w;i--)
	{
	s=s+e[i];
	s2=s2+c[i];
	}
out<<s2;

in.close();
out.close();
return 0;
}