#include<fstream>
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int mini=7777777,n,m,i,j,w,x,y,v[50001];
int main()
{
    f>>n>>w;
    for(i=1;i<=n;++i)
    {
        f>>x>>y;
        for(j=m;j>=1;--j)
        if(v[j]&&j+x<=50000)
        if(v[j+x]>v[j]+y||v[j+x]==0)
        v[j+x]=v[j]+y;
        if(v[x]>y||v[x]==0)
        v[x]=y;
        if(m+x<=50000)
        m=m+x;
    }
    for(i=w;i<=50000;++i)
    if(v[i]&&v[i]<mini)
    mini=v[i];
    if(mini==7777777)
    mini=-1;
    g<<mini<<'\n';
    return 0;
}