#include <fstream>

using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int v[1001][5001],e,c,E,n,i,j;
int main()
{
    f>>n>>E;
    for(i=0;i<=n;i++)
       for (j=1;j<=E;j++)
       v[i][j]=(1<<31-1);
      for (i=1;i<=n;i++)
      {
        f>>e>>c;
        for (j=1;j<=E;j++)
        if (e>E) v[i][j]=min(v[i-1][j],c);
        else v[i][j]=min(v[i-1][j],v[i-1][j-e]+c);
      }
    if (v[n][E]==(1<<31-1)) g<<'-1'<<'\n';
    else g<<v[n][E]<<'\n';
    return 0;
}