#include<fstream>
#define M 20000000
using namespace std;
int d[15001];
void init()
{
    for (int i=1;i<15001;++i)
        d[i]=M;
}
int main()
{
    ifstream in ("energii.in");
    ofstream out ("energii.out");
    int w,g,i,mn,v,c;
    in>>g>>w;
    init();
    d[0]=0;
    for (i=0;i<g;++i)
        {
        in>>v>>c;
        for (int j=15000-v;j>-1;--j)
            if (d[j+v]>d[j]+c)
                d[j+v]=d[j]+c;
        }
    mn=M;
    for (i=w;i<15001;++i)
        if (mn>d[i])
            mn=d[i];
    if (mn==M)
        mn=-1;
    out<<mn<<'\n';
    in.close();
    out.close();
    return 0;
}