program energiii;
type vector=array[1..1001]of integer;
type energii=record
     c,e:vector;
end;
var e,c:vector;
    f,g:text;
    a,b:energii;
    n,w,i,j,k,min:longint;

procedure calculare(i:longint);
var j,k:longint;
begin
  b.e[i]:=e[i];
  b.c[i]:=c[i];
  if b.e[i]>=w then
   if b.c[i]<min then
    min:=b.c[i];
  for j:=i+1 to n do
   begin
     b.e[j]:=a.e[j]-a.e[j-1]+b.e[j-1];
     b.c[j]:=a.c[j]-a.c[j-1]+b.c[j-1];
     if b.e[j]>=w then
      if b.c[j]<min then
       min:=b.c[j];
   end;
  a.e:=b.e;
  a.c:=b.c;
  if i<n then
   calculare(i+1);
end;

begin
  assign(f,'energii.in');
  reset(f);
  readln(f,n);
  readln(f,w);
  for i:=1 to n do
   readln(f,e[i],c[i]);
  close(f);

  min:=maxlongint;
  for j:=1 to n do
   begin
     for k:=1 to j do
      begin
        a.e[j]:=a.e[j]+e[k];
        a.c[j]:=a.c[j]+c[k];
      end;
     if a.e[j]>=w then
       if a.c[j]<min then
        min:=a.c[j];
   end;
  calculare(2);
  assign(g,'energii.out');
  rewrite(g);
  if min<>maxlongint then
   write(g,min) else
   write(g,'-1');
  close(g);
end.