#include <iostream>
#include<fstream>
using namespace std;

ifstream f("energii.in");
ofstream g("energii.out");

#define inf 20000000

///struct centrala
///{
   /// int energie, cost;
///};
int n,w,i,j,pd[1000000000],e,cost,s,minn;
///centrala e[1001];
int main()
{
    f>>n>>w;
    for(i=1;i<=1000000000;++i) pd[i]=inf;
    for(i=1;i<=n;++i)
    {
        f>>e>>cost;
        s+=e;
        for(j=1000000000;j>=1;--j)
                    pd[j+e]=min(pd[j+e], pd[j]+cost);

         pd[e]=min(pd[e],cost);
    }
    if(s<w)
        g<<-1;
    else
    {
        minn=inf;
        for(i=w;i<=1000000000;++i)
            minn=min(minn,pd[i]);
        g<<minn;
    }
    f.close();
    g.close();
    return 0;
}