#include <fstream>

using namespace std;
const int GMAXX=5000;
const int INF=2000000000;
int d[GMAXX+5];
struct CENTRALA
{
    int e,c;
};
CENTRALA v[1005];
ifstream cin("energii.in");
ofstream cout("energii.out");
int main()
{
    int n,i,j,last,minim,GMAX;
    cin>>n>>GMAX;
    minim=INF;
    for(i=1;i<=n;i++)
        cin>>v[i].e>>v[i].c;
    for(i=1;i<=GMAX;i++)
            d[i]=INF;
     d[0]=0;
     last=0;

     for(i=1;i<=n;i++)
     {
        for(j=last;j>=0;j--)
     {
         if(d[j]!=INF && j+v[i].e<=GMAX && d[j+v[i].e]>d[j]+v[i].c)
            d[j+v[i].e]=d[j]+v[i].c;
         if(j+v[i].e>=GMAX && d[j]!=INF && minim>d[j]+v[i].c)
            minim=d[j]+v[i].c;
     }
     last=min(last+v[i].e,GMAX);
     }
     if(minim==INF)
        cout<<-1;
     else
        cout<<minim;

    return 0;
}