#include<iostream>
#include<fstream>
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
short N,W,i,j,t,min1;
short e[1002],c[1002];
int rez[500001];

int main()
{
    f>>N>>W;
    for (i=1;i<=N;i++)
        {f>>e[i]>>c[i];t+=e[i];}
    if (t<W)
        g<<-1;
    else
    {
        for (i=0;i<=15002;i++)
            rez[i]=350000;
        rez[0]=0;
        for (i=1;i<=N;i++)
        {
            for (j=W;j>=0;j--)
            {
                if (rez[j]!=350000)
                {
                    if (rez[j+e[i]]==350000 || rez[j+e[i]]>rez[j]+c[i])
                        rez[j+e[i]]=rez[j]+c[i];
                }
            }
        }
        min1=350000;
        for (i=W;i<=W+10001;i++)
            if (rez[i]<min1) min1=rez[i];
        //for (i=1;i<=W;i++)
        //    cout<<rez[i]<<'\n';
        g<<min1;
    }
    f.close();g.close();
    return 0;
}