#include <fstream>

using namespace std;

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

const int WMax = 10000, NMax = 1000, oo = 1e8;
int DP[WMax + 5], N, W, K, Sol = 1e8, G[NMax + 5], C[NMax + 5];

int main()
{
    fin >> N >> W;

    for(int i = 1, w, c; i <= N; i++)
    {
        fin >> w >> c;

        if(w < W)
            G[++K] = w, C[K] = c;
        else
            Sol = min(Sol, c);
    }
    for(int i = 1; i <= WMax; i++)
        DP[i] = oo;

    for(int i = 1; i <= K; i++)
    {
        for(int j = WMax; j >= G[i]; j--)
            DP[j] = min(DP[j - G[i]] + C[i], DP[j]);
    }

    for(int i = W; i <= WMax; i++)
        Sol = min(Sol, DP[i]);

    fout << Sol << '\n';

    fin.close();
    fout.close();

    return 0;
}