#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;

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

const int Emax = 10001;
const int Nmax = 1001;
const int Wmax = 5001;
const int INF = 0x3f3f3f3f;

int n, w, maxe;
int E[Nmax], C[Emax];
vector<int> Cost;

int main()
{
    is >> n >> w;
    for ( int i = 1; i <= n; ++i )
    {
        is >> E[i] >> C[i];
        maxe = max(maxe, E[i]);
    }
    Cost = vector<int>(w + maxe + 2, INF);
    Cost[0] = 0;
    for ( int i = 1; i <= n; ++i )
        for ( int j = w; j >= 0; --j )
            if ( Cost[j] != INF && Cost[j + E[i]] > Cost[j] + C[i] )
                Cost[j + E[i]] = Cost[j] + C[i];
    int r;
    r = *min_element(Cost.begin() + w, Cost.end());
    if ( r == INF )
        os << -1;
    else
        os << r;
    is.close();
    os.close();
    return 0;
}