# include <fstream>
using namespace std;
int G,W,E[5002],C[5003],i,j,M[5003][5003];

ifstream cin("energii.in");
ofstream cout("energii.out");
int main()
{
    cin >>  G >> W;
    for(i=1;i<=G;++i)
    cin >> E[i] >> C[i];
      for(i=0;i<=G;++i)
      for(j=0;j<=W;++j)
            M[i][j]=1000001;
    for(i=1;i<=G;++i)
    for(j=1;j<=W;++j)
    {
        if(E[i]<j)
        {
            M[i][j]=min(M[i-1][j],M[i-1][j-E[i]]+C[i]);
        }
        else
        {
            M[i][j]=min(M[i-1][j],C[i]);
        }
    }
    cout <<  M[G][W];
    return 0;
}