#include <fstream>

using namespace std;
int dp[1001][10001], cost[1001], en[1001], W, n;
const int oo = 1E9;
ifstream fin ("energii.in");
ofstream fout ("energii.out");
int main()
{
    int sum = 0, m;
    fin >> n >> W;
    for (int i = 1; i <= n; i++)
    {
        fin >> en[i] >> cost[i];
        sum += en[i];
    }
    if (sum < W)
    {
        fout << "-1\n";
        fout.close();
        return 0;
    }
    for (int i = 1;  i <= n; i++)
        for (int j = 1; j <= W + 1000; j++)
            dp[i][j] = oo;
    dp[1][en[1]] = cost[1];
    for (int i = 2; i <= n; i++)
        for (int j = 1; j <= W + 1000; j++)
        {
            m = dp[i - 1][j];
            if (j >= en[i] && m > dp[i - 1][j - en[i]] + cost[i])
                m = dp[i - 1][j - en[i]] + cost[i];
            dp[i][j] = m;
        }
    int ans = oo;
    for (int i = W; i <= W + 1000; i++)
        if (dp[n][i]) ans = min(ans, dp[n][i]);
    fout << ans << "\n";
    fout.close();
    return 0;
}