#include <cstdio>
using namespace std
#define N 20001
#define M 1001
int main()
{
   int G,W,E[M],C[M],v[N]={0},c[N]={0},i,j,l,ult;
   v[0]=-1;
   freopen("energii.in", "r", stdin);
   freopen("energii.out", "w", stdout);
   scanf("%d", &G);
   scanf("%d", &W);
   for(i=1;i<=G;i++)
   {
       scanf("%d", &E[i]);
       scanf("%d", &C[i]);
   }
   ult=0;
   for(i=1;i<=G;i++)
     for(j=ult;j>=0;j--)
     {
	  if(v[j+E[i]]!=0 && c[j+E[i]]>C[i])
	     c[j+E[i]]=C[i];
	  if(v[j]!=0 && v[j+E[i]]==0)
	  {
	      v[j+E[i]]=E[i];
	      c[j+E[i]]=c[j]+C[i];
	      if(j+E[i]>ult)
		ult=j+E[i];
	  }
	  if(ult>=W)
	   if(c[W])
	   { printf("%d", c[w]); return 0;}
	   else
	   {
	      l=W;
	      while(!c[l])
	       l++;
	      printf("%d", c[l]);
	      return 0;
	   }
     }
   printf("%d", -1);
   return 0;
}