#include <fstream.h>
long a[100000];

int main()
  {
   int n,w,x,y,i,j;
   long se,sc,min=-1,max=0;
   ifstream f("energii.in");
   ofstream g("energii.out");
   f>>n>>w;
   for (i=1;i<=n;i++)
     {
      f>>x>>y;
      for (j=max;j>=0;j--)
	{
	 if (a[j]!=0)
	   {
	    se=j+x;
	    sc=a[j]+y;
	    if (se>=w && (min>sc || min==-1))
	      min=sc;
	    else
	      {
	       if (a[se]==0 || (a[se]!=0 && a[se]>a[j]+y))
		 a[se]=a[j]+y;
	      }
	   }
	}
      if (x>=w && (min>y || min==-1))
	min=y;
      else
	if (a[x]==0 || (a[x]!=0 && a[x]>y))
	  a[x]=y;
      if (max+x>5001)
	max=5001;
      else
	max=max+x;

     }

   g<<min<<"\n";
   f.close();
   g.close();
   return 0;
  }