#include<fstream>
using namespace std;
int main()
{int G,W,e[100],c[100],o[100],i,t,aux,j;
float ef[100],total;
fstream f("energii.in",ios::in);
fstream g("energii.out",ios::out);
f>>G;
f>>W;
for(i=1;i<=G;i++)
	f>>e[i]>>c[i];
for(i=1;i<=G;i++)
{float(ef[i]=e[i]/c[i]);
o[i]=i;}
for(i=1;i<=G-1;i++)
	for(j=i+1;j<=G;j++)
		if(ef[o[i]]<ef[o[j]]){aux=o[i];
	                          o[i]=o[j];
							 o[j]=aux;}
		total=0;
		t=1;
		while(e[o[t]]<W)
		{total=total+c[o[t]];
		 W=W-e[o[t]];
		 t++;
		}
		g<<total;
		g<<endl;
		return 0;
}