#include <iostream>
#include <fstream>
#define dMAX 5000
#define INF 10005

using namespace std;

int n, energyNeeded;
int energy, cost;
int arr[dMAX + 5];

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

int main()
{
    int i, j;
    fin >> n >> energyNeeded;
    for (i = 1; i <= dMAX; i++) arr[i] = INF;
    for (i = 1; i <= n; i++) {
        fin >> energy >> cost;
        for (j = energyNeeded; j >= 0; j--) {
            arr[min(j + energy, energyNeeded)] = min(arr[j + energy, energyNeeded], arr[j] + cost);
        }
    }
    if (arr[energyNeeded] == INF) fout << -1;
    else fout << arr[energyNeeded];
    return 0;
}