#include <fstream>

#define NMAX 10005
#define NMAXIM 1000000005

using namespace std;

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

int n,i,j,power,rez=NMAXIM;
int  v[NMAX],t[NMAX],c[NMAX];

int main()
{
    f>>n>>power;
    for(i=1;i<=n;i++)
    {
        f>>v[i]>>c[i];
    }
    for(i=1;i<=power+NMAX;i++)
        t[i]=-1;
    for(i=1;i<=n;i++)
    {
        for(j=power;j>=0;j--)
        {
            if(t[j+v[i]]>t[j]+c[i]||t[j+v[i]]==-1)
                if(t[j]!=-1)
                    t[j+v[i]]=t[j]+c[i];
        }
    }
    for(i=power;i<=power+NMAX;i++)
        if(t[i]!=-1)
            rez=min(rez,t[i]);
    if(rez==NMAXIM)
        g<<"-1";
    else
        g<<rez;
    return 0;
}