#include <bits/stdc++.h>
#define Inf 10000001
using namespace std;
ifstream in ("energii.in");
ofstream out ("energii.out");
struct info
{
    int cost;
    int energie;
};
info v[1001];
int rasp[Inf];
int main ()
{
    int g,w,s=0;
    in>>g>>w;
    for (int i=1;i<=g;++i)
        {
            in>>v[i].energie>>v[i].cost;
            s+=v[i].energie;
        }
    if (s<w)
    {
        out<<'-1';
        return 0;
    }
    for (int i=1;i<=s;++i)
        rasp[i]=Inf;
    for (int i=1;i<=g;++i)
    {
        for(int j=w; j>=0; --j)
            rasp[min(w, j+v[i].energie)]=min(rasp[min(w, j+v[i].energie)], rasp[j]+v[i].cost);
    }
    out<<rasp[w];
    return 0;
}