#include <fstream>

using namespace std;

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

int p[1001], w[1001], a[5001];

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