#include <fstream>
#include <string.h>
#include <vector>

using namespace std;

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

const int oo = 0x3f3f3f3f;

int e, c, n, g, w;

int main()
{
    fin >> g >> w;
    vector<int> optim(2 * w + 1, oo);
    optim[0] = 0;

    while (g--)
    {
        fin >> e >> c;
        for (int i = 2 * w - e; i >= 0; --i)
            optim[i + e] = min(optim[i + e], optim[i] + c);
    }

    int sol = oo;

    for (int i = w; i <= 2 * w; ++i)
        sol = min(sol, optim[i]);

    if (sol == oo)
        sol = -1;

    fout << sol << "\n";

    return 0;
}