#include <fstream>

using namespace std;

int n,w,d[10001],i,e[10001],c[10001],j,x;

ifstream fin ("energii.in");
ofstream fout ("energii.out");

int main ()
{
    fin>>n>>w;
    for (i=1;i<=n;i++)
        fin>>e[i]>>c[i];
    for (i=1;i<=10000;i++)
        d[i]=100000000;
    x=100000000;
    d[0]=0;
    for (i=1;i<=n;i++)
        for (j=w-1;j>=0;j--)
            if (d[j]!=x)
            {
                if (j+e[i]<w)
                    d[j+e[i]]=min(d[j+e[i]],d[j]+c[i]);
                else
                    d[w]=min(d[w],d[j]+c[i]);
            }
    if (d[w]!=x)
        fout<<d[w]<<"\n";
    else
        fout<<-1;
    return 0;
}