#include<iostream>
using namespace std;
int greu[10001],pierd[10001],castig[1000000],i,n,s=999999999,cautat,smax,j;
#include<fstream>
ifstream f("energii.in");
ofstream g("energii.out");
int main()
{
   f>>n>>cautat;
    for(i=1;i<=n;i++)
    {f>>greu[i]>>pierd[i];
        smax=smax+greu[i];
    }

    for(i=1;i<=n;i++)
        for(j=smax-greu[i];j>=0;j--)
            if(castig[j+greu[i]]>castig[j]+pierd[i])
        {
            castig[j+greu[i]]=castig[j]+pierd[i];
        }
        int maximul=999999999;
        for(i=cautat;i<=smax;i++)
            if(maximul>castig[i])
                maximul=castig[i];
      if(maximul!=999999999)
      g<<maximul;
      else
        g<<"-1";
}