#include <iostream>
#include <vector>
#include <array>
#include <climits>
#include <fstream>

using namespace std;

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

int minimum_cost(int number_of_generators, int necessary_power, const vector<int> &generator_power,
                 const vector<int> &generator_cost) {
    vector<vector<int> > dp(necessary_power + 1, vector<int>(number_of_generators + 1, INT_MAX / 2 - 1));

    for (int i = 1; i <= necessary_power; i++) {
        if(generator_power[1] >= i){
            dp[i][1] = generator_cost[1];
        }
    }

    for (int i = 1; i <= necessary_power; i++) {
        for (int j = 2; j <= number_of_generators; j++) {

            if (generator_power[j - 1] >= i) {
                dp[i][j] = min(
                        generator_cost[j - 1],
                        dp[i][j - 1]
                );
            } else {
                dp[i][j] = min(
                        dp[i][j - 1],
                        dp[i - generator_power[j - 1]][j - 1] + generator_cost[j - 1]
                );
            }
        }
    }
    return dp[necessary_power][number_of_generators];
}

int main() {
    int number_of_generators;
    int necessary_power;
    fin >> number_of_generators >> necessary_power;
    vector<int> generator_power(number_of_generators);
    vector<int> generator_cost(number_of_generators);
    for (int i = 0; i < number_of_generators; i++) {
        fin >> generator_power[i];
        fin >> generator_cost[i];
    }
    fout << minimum_cost(number_of_generators, necessary_power, generator_power, generator_cost);
    return 0;
}