#include <iostream>
#include <fstream>

#define WMAX 5000001

using namespace std;

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

int G;
int W;
int V[5002];

int main()
{
    fin>>G>>W;
    for(int i=1;i<=W;i++)
        V[i] = WMAX;
    for(int i=1;i<=G;i++)
    {
        int x,y;
        fin>>x>>y;

        for(int j=W;j>=0;j--)
        {
            if (j + x < W) {
                V[j+x] = min(V[j+x], V[j]+y);
            }else
            {
                V[W] = min(V[W],V[j]+y);
            }
        }
    }

    if (V[W] == WMAX)
        fout<<-1;
    else
        fout<<V[W];

    return 0;
}