#include <fstream>
#include <vector>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
int n,w,maxx,scost;
const int lim=1003;
struct generator
{
    int e,cost;
}v[lim];
vector<pair<int,int> > f;
int main()
{
    ios_base::sync_with_stdio(false);
    in.tie(0),out.tie(0);
    in>>n>>w;
    for(int i=1;i<=n;++i)
    {
        in>>v[i].e>>v[i].cost;
        maxx+=v[i].e;
        scost+=v[i].cost;
    }
    if(maxx<w)
    {
        out<<-1;
        return 0;
    }
    if(maxx==w)
    {
        out<<scost;
        return 0;
    }
    f.push_back({0,0});
    for(int i=1;i<=n;++i)
    {
        for(int j=f.size()-1;j>=0;--j)
        if(f[j].first<w)
        {
            f.push_back({f[j].first+v[i].e,f[j].second+v[i].cost});
        }
    }
    int minn=0x7fffffff;
    for(int j=f.size()-1;j>=0;--j)
        if(f[j].second<minn and f[j].first>=w)
        minn=f[j].second;
    out<<minn;
    return 0;
}