#include <fstream>
#include <vector>
#include <algorithm>
#include <climits>

using namespace std;

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

int main() {
    int G, W;
    fin >> G >> W;
    vector<int> dp(W + 1, INT_MAX); 
    dp[0] = 0; 
    for (int i = 0; i < G; ++i) {
        int EGi, CGi;
        fin >> EGi >> CGi;
        for (int j = W; j >= EGi; --j) {
            if (dp[j - EGi] != INT_MAX) {
                dp[j] = min(dp[j], dp[j - EGi] + CGi);
            }
        }
    }
    int Cmin = INT_MAX;
    for (int j = W; j <= W; ++j) {
        Cmin = min(Cmin, dp[j]);
    }
    if (Cmin == INT_MAX) {
        fout << -1 << "\n";
    } else {
        fout << Cmin << "\n";
    }
    return 0;
}