#include <fstream>
#define min 100000000

using namespace std;

unsigned long g,w,v[1000],u[1000];
long long m=min;
void cautare(unsigned long i,unsigned long S,unsigned long C)
{
    if(S>=w && C<m)
    m=C;
    else
    for(;i<=g;i++)
    cautare(i+1,S+v[i],C+u[i]);
}
int main()
{
    unsigned long i;
    fstream f("energii.in",ios::in);
    fstream o("energii.out",ios::out);
    f>>g>>w;
    for(i=1;i<=g;i++)
    f>>v[i]>>u[i];
    for(i=1;i<=g;i++)
    cautare(i,0,0);
    if(m==min)
    o<<-1;
    else
    o<<m;
    f.close();
    o.close();
    return 0;
}