#include <fstream>
#define VAL 5005
#define INF 2000000000

using namespace std;

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

int N, G, e;
int c, i, j;
int dp[VAL];

int main()
{
    fin >> N >> G;
    for (i=1; i<=G; i++)
      dp[i]=INF;
    for (i=1; i<=N; i++)
    {
        fin >> e >> c;
        for(j=G; j>=0; j--)
        {
            if (j<=e)
              dp[j]=min(dp[j], c);
            else
              dp[j]=min(dp[j], dp[j-e]+c);
        }
    }
    if (dp[G]!=INF)
      fout << dp[G] << '\n';
    else
      fout << -1 << '\n';
    fin.close();
    fout.close();
    return 0;
}