#include <fstream>
using namespace std;
ifstream fin ("energii.in");
ofstream fout ("energii.out");
int n,g,i,j,a[1001],b[1001],f[5001];
int main()
{
    fin>>n>>g;
    for (i=1; i<=n; i++)
        fin>>a[i]>>b[i];
    for (i=0; i<=5000; i++)
        f[i]=-1;
    for (i=1; i<=n; i++)
    {
        for (j=g-1; j>0; j--)
        {
            if (f[j]!=-1)
            {
                if (j+a[i]<=g)
                {
                    if (f[j+a[i]]>f[j]+b[i]||f[j+a[i]]==-1)
                        f[j+a[i]]=f[j]+b[i];
                }
                else if (f[g]>f[j]+b[i]||f[g]==-1)
                    f[g]=f[j]+b[i];
            }
        }
        if (a[i]<=g)
        {
            if (f[a[i]]>b[i]||f[a[i]]==-1)
                f[a[i]]=b[i];
        }
        else if (f[g]>b[i]||f[g]==-1)
            f[g]=b[i];
    }
    if (f[g]!=-1)
        fout<<f[g];
    else
        fout<<-1;
    return 0;
}