#include <iostream>
#include <fstream>
using namespace std;
int n, w, i, a[20], b[20], j, aux, s, k, su, x;
int main()
{
    ifstream f ("energii.in");
    ofstream g ("energii.out");
    f>>n;
    f>>w;
    for (i=1; i<=n; i++)
    {
            f>>a[i];
            f>>b[i];
    }
    for (i=1; i<n; i++)
    {   for (j=i+1; j<=n; j++)
        {   if (a[i]>a[j])
            {   aux=a[i];
                a[i]=a[j];
                a[j]=aux;

                aux=b[i];
                b[i]=b[j];
                b[j]=aux;
            }   }   }
    for (i=n; i>=1; i--)
    {
        if (a[i]>=w) s=b[i];
    }
    if (s==0)
    {   for (i=1; i<=n; i++)
        {   if (su<=w)  {
            su=su+a[i];
            s=s+b[i];   }
        }   }
    x=-1;
    if (s>=w)
    g<<s;
    else g<<x;

}