#include<fstream.h>
int main()
{
 int s1,n,m,a[1111],v[1111],i,j,aux1,s;
 float r[1111],aux;
 ifstream f("energii.in");
 ofstream g("energii.out");
  f>>n;
  f>>m;
 for(i=1;i<=n;i++)
 {
  f>>a[i];
  f>>v[i];
 }
 for(i=1;i<=n;i++)
  r[i]=(float)a[i]/v[i];
 for(i=1;i<n;i++)
  for(j=i+1;j<=n;j++)
  if(r[i]<r[j])
  {
	aux=r[i];
	r[i]=r[j];
	r[j]=aux;
	aux1=a[i];
	a[i]=a[j];
	a[j]=aux1;
	aux1=v[i];
	v[i]=v[j];
	v[j]=aux1;
  }
 i=1;
 s=0;
 s1=0;
 while(s<m && i<n)
 {
  s=s+a[i];
  s1=s1+v[i];
  i++;
 }
 if(s<m)
  g<<"-1";
 else
 g<<s1;
 return 0;
}