#include <bits/stdc++.h>

using namespace std;

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

int n, G;
int w[1001], p[1001], sol[5010];

int main()
{
    in >> n >> G;
    for (int i = 1; i <= n; ++i)
        in >> w[i] >> p[i];
    for (int i = 1; i <= G; ++i)
        sol[i]=100010;
    sol[0] = 0;
    for (int i = 1; i <= n; ++i)
    {
        for (int j = G; j >= w[i]; --j)
        {
            if (sol[j - w[i]] + p[i] < sol[j])
                sol[j] = sol[j - w[i]] + p[i];
        }
        for (int j = 1; j <= w[i]; ++j)
        {
            if (sol[j] > p[i])
                sol[j] = p[i];
        }
    }
    if (sol[G] == 100010)
        out << "-1\n";
    else
        out << sol[G] << "\n";
    return 0;
}