#include <iostream>
#include <fstream>
using namespace std;

int n, w, cMin[10005], e, c;

int main()
{
    ifstream cin("energii.in");
    ofstream cout("energii.out");

    for (int i = 1; i <= 10004; i++)
        cMin[i] = 10000000;
    
    cin >> n >> w;
    for (int i = 1; i <= n; ++i)
    {
        cin >> e >> c;

        for (int j = 10004; j >= e; --j)
            cMin[j] = min(cMin[j], cMin[j - e] + c);
    }
    int minv = 100000001;
    for (int i = 10004; i >= w; --i)
        minv = min(minv, cMin[i]);

    if (minv == 100000000)
        cout << "-1";
    else
        cout << minv;

    return 0;
}