#include <fstream>

using namespace std;

const int N = 1001;
const int W = 5001;

int cost[W+1], en[N], c[N];

int main()
{
    ifstream in("energii.in");
    ofstream out("energii.out");
    int n, w;
    in >> n >> w;
    for (int i = 0; i < n; i++)
    {
        in >> en[i] >> c[i];
    }
    ///initializam vectorul cost
    cost[0] = 0;
    int cost_min = 1e7;
    for (int j = 1; j <= w; j++)
    {
        cost[j] = cost_min;
    }
    for (int i = 0; i < n; i++)
    {
        for (int j = w; j >= w - en[i]; j--)
        {
            if (cost[j] != 1e7)
            {
                cost[j + en[i]] = min(cost[j + en[i]], cost[j] + c[i]);
            }
        }
    }
    /*
    for (int j = 1; j <= w; j++)
    {
        cost_min = min(cost_min, cost[j]);
    }
    */

    out << cost[w] << "\n";
    in.close();
    out.close();
    return 0;
}