#include <fstream>

using namespace std;

ifstream cin("energii.in");
ofstream cout("energii.out");

int n, en, e[1002], c[1002], rez[5003];

int main()
{
    cin >> n >> en;
    for (int i = 1; i <= n; i++)
        cin >> e[i] >> c[i];
    for (int i = 0; i <= en; i++)
        rez[i]=2e9;

    for (int i = 1; i <= n; i++)
        for (int j = en; j >= 0; j--)
            if (j <= e[i])
                rez[j] = min(rez[j], c[i]);
            else
                rez[j] = min(rez[j], rez[j - e[i]] + c[i]);
    if (rez[en] == 2e9)
        cout << -1;
    else
        cout << rez[en];
    return 0;
}