# include <fstream>
# include <algorithm>
# include <cstring>

using namespace std;

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

int C[5005];
int n,G,i,j,E,cost;

int main ()
{
    f >> n >> G;
    for (i = 1; i <= G; i++)
        C[i] = 100000;

    for (i = 1; i <= n; i++)
    {
        f >> E >> cost;
        for (j = G; j >= 1; j--)
        {
            if (E >= j) C[j] = min(C[j],cost);
            else C[j] = min(C[j],C[j-E] + cost);
        }
    }
    if (C[G] == 100000) g << "-1\n";
    else g << C[G] <<"\n";

    return 0;
}