var e, c:array [1..1001] of longint;
    chk:array [1..5001] of longint;
    buf1:array [1.. 1 shl 17] of char;
    et, ct:array [0..5001] of longint;
    i, j, n, t, min, aux, k, l:longint;
    f, g:text;

procedure qsort (st, dr:longint);
var s, d, p:longint;
  begin
  if dr-st>=1 then
    begin
    s:=st; d:=dr;
    p:= e[random (dr-st)+st];
    while s< d do
      begin
      while e[s]<p do s:=s+1;
      while e[d]>p do d:=d-1;
      if s<=d then
        begin
        aux:=e[s]; e[s]:=e[d]; e[d]:=aux;
        aux:=c[s]; c[s]:=c[d]; c[d]:=aux;
        s:=s+1; d:=d-1;
        end;
      end;
    if st<d then qsort (st, d);
    if s<dr then qsort (s, dr);
    end;
  end;


begin
assign (f, 'energii.in'); settextbuf (f, buf1); reset (F);
assign (g, 'energii.out'); rewrite (g);

readln (f, n);
readln (f, t);
for i := 1 to n do
  begin
  read (f, e[i], c[i]);
  end;

qsort (1, n);

k:=0; min:=maxlongint;
l:=0;
for i := 1 to n do
  begin
  for j := 0 to l do
    begin
    if et[j]+e[i] < t then
      begin
      if chk[et[j]+e[i]] <> 0  then
        begin
        if ct[j]+c[i] < chk[et[j]+e[i]] then chk[et[j]+e[i]] := ct[j]+c[i];
        end
                               else
        begin
        k:=k+1;
        ct[k]:=ct[j]+c[i];
        et[k]:=et[j]+e[i];
        chk[et[j]+e[i]]:=ct[j]+c[i];
        end;
      end
                      else
      begin
      if ct[j]+c[i] < min then min := ct[j]+c[i];
      end;
    end;
  l:=k;
  end;

if min = maxlongint then writeln (g, '-1')
                    else writeln (g, min);
close (f); close (g);
end.