#include <fstream>
std::ifstream fin("energii.in");
std::ofstream fout("energii.out");
const int inf = 1e8;
int dp[1001][5001];
int main() {
    int n, w;
    fin >> n >> w;
    for (int i = 0; i <= n; i++){
        for (int j = 0; j <= w; j++){
            dp[i][j] = inf;
        }
    }
    dp[0][0] = 0;
    for (int i = 1; i <= n; i++) {
        int energie, cost;
        fin >> energie >> cost;
        for (int j = 0; j <= w; j++) {
            int previous = j - energie;
            if (previous < 0)
                previous = 0;
            dp[i][j] = std::min(dp[i - 1][j], dp[i - 1][previous] + cost);
        }
    }
    if (dp[n][w] != inf){
        fout << dp[n][w];
    } else {
        fout << -1 << " ";
    }
    return 0;
}