#include <fstream>

using namespace std;

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

const int E = 5000;
const int INF = 1e9;

int cost[E+1];

int main() {
    int e, n;
    in >> n >> e;
    for (int j = 1; j <= e; j++) {
        cost[j] = INF;
    }
    for (int i = 0; i < n; i++) {
        int e_i, c_i;
        in >> e_i >> c_i;
        for (int j = e - 1; j >= 0; j--) {
            if (cost[j] != INF) {
                if (j + e_i >= e) {
                    cost[e] = min(cost[e], cost[j] + c_i);
                }
                else {
                    cost[j + e_i] = min(cost[j + e_i], cost[j] + c_i);
                }
            }
        }
    }
    if (cost[e] == INF) {
        cost[e] = -1;
    }
    out << cost[e];
    in.close();
    out.close();
    return 0;
}