#include <fstream>
#include <algorithm>
using namespace std;

int n,gr,w[5001],p[5001],i,v[2][10001],j,k,s,t,i1;
int main()
{
    ifstream f("energii.in");
    ofstream g("energii.out");

    f>>n>>gr;
    s=0;
    for (i=0;i<n;i++)
        {
            f>>w[i]>>p[i];
            s=s+w[i];
        }
    if (s>=gr)
    {
    k=1;
    for (i=0;i<n;i++)
        {
            k=1-k;
            for (i1=0;i1<s;i1++)
                {
                    v[1-k][j]=v[k][j];
                    if (w[i1]<=i1) v[1-k][j]=min(v[1-k][i1],v[k][i1-w[i1]]+p[i1]);
                }
        }
    t=0;
    while (t<gr || v[1-k][t]==0) t++;
    g<<v[1-k][t];
    }
    else
    {
    g<<"-1";
    }
    f.close();
    g.close();
    return 0;
}