# include <stdio.h>   
long int s,n,min,a[1000],b[1000],i,j,aux,s2;
int main ()
{
freopen ("energii.in","r",stdin);
freopen ("energii.out","w",stdout);
scanf ("%li",&n);
scanf ("%li",&min);
for (i=0;i<n;i++)
{
scanf ("%li",&a[i]);
scanf ("%li",&b[i]);       
}
for (i=0;i<n-1;i++)
for (j=i+1;j<n;j++)
if (b[i]<b[j])
{
aux=a[i];
a[i]=a[j];
a[j]=aux;
aux=b[i];
b[i]=b[j];
b[j]=aux;
}
for (i=0;i<n;i++)
s=s+a[i];
if (s<min)
printf ("-1");
else
{
for (i=0;i<n;i++)
{
s=s+a[i];
s2=s2+b[i];
if (s>=min)
{
printf ("%li",s2);
break;
}
}
}
return 0;
}