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

ifstream fin("energii.in");
ofstream fout("energii.out");

const int INF = (1 << 30);
int G,W;
int mat[5010];
int x,y;
vector <int> L;
void Read()
{
    fin>>G>>W;
    for(int i=1;i<=5002;++i)
        mat[i]=INF;
    for(int i=1;i<=G;++i)
    {
        fin>>x>>y;
        int l,c;
        int n=L.size();
        for(int k=0;k<n;++k)
        {
            l=L[k];
            mat[l+x]=min(mat[l+x],mat[l]+y);
            L.push_back(l+x);
        }
        mat[x]=min(mat[x],y);
        L.push_back(x);
    }
    int cost=INF;
    for(int i=W;i<=5002;++i)
        //fout<<mat[i]<<"\n";
        cost=min(cost,mat[i]);
    if(cost!=INF)fout<<cost;
    else fout<<-1;
}
int main()
{
    Read();
    return 0;
}