#include <fstream>

using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
const int GMAXX=5000;
const int LNF=2000000000;
int d[GMAXX+5];
struct centrala
{
    int e,c;
};
centrala v[1005];
int main()
{
    int n,i,j,last,minim,GMAX;
    fin>>n>>GMAX;
    for(i=1;i<=n;i++)
        fin>>v[i].e>>v[i].c;
    for(i=1;i<=GMAX;i++)
        d[i]=LNF;
    last=0;
    for(i=1;i<=n;i++)
        for(j=last;j>=0;j--)
        {
            if(d[j]!=LNF && j+v[i].e<=GMAX && d[j+v[i].e]>d[j]+v[i].e)
                d[j+v[i].e]=d[j]+v[i].e;
            if(j+v[i].e>=GMAX && d[j]!=LNF && minim>d[j]+v[i].c)
                minim=d[j]+v[i].c;
            last=min(last+v[i].e,GMAX);
        }
    if(minim==LNF)
        fout<<-1;
    else
        fout<<minim;
    return 0;
}