#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
#include <climits>
using namespace std;

int main() {
    ifstream infile("energii.in");
    ofstream outfile("energii.out");

    int G, W;
    infile >> G >> W;

    vector<int> E(G);
    vector<int> C(G);
    for (int i = 0; i < G; ++i) {
        infile >> E[i] >> C[i];
    }

    vector<int> dp(W + 1, INT_MAX);
    dp[0] = 0;

    for (int i = 0; i < G; ++i) {
        for (int j = W; j >= E[i]; --j) {
            if (dp[j - E[i]] != INT_MAX) {
                dp[j] = min(dp[j], dp[j - E[i]] + C[i]);
            }
        }
    }

    if (dp[W] == INT_MAX) {
        outfile << -1 << endl;
    } else {
        outfile << dp[W] << endl;
    }

    infile.close();
    outfile.close();

    return 0;
}