var g,w,i,j,k,n:longint;
    e,c,a:array[0..10002] of longint;
    
begin
  assign(input,'energii.in');
  assign(output,'energii.out');
  reset(input);
  rewrite(output);
  read(g,w);
  for i:=1 to g do
    read(e[i],c[i]);
  for i:=1 to w*2 do a[i]:=-1;
  for i:=1 to g do begin
    for j:=w*2-e[i] downto 1 do begin
      if a[j]<>-1 then 
        if (a[j+e[i]]>a[j]+c[i]) or (a[j+e[i]]=-1) then
          a[j+e[i]]:=a[j]+c[i];
    end;
    if (a[e[i]]>c[i]) or (a[e[i]]=-1) then
      a[e[i]]:=c[i];
  end;
  k:=a[w];
//  for i:=1 to w*2 do write(a[i],' ');
//  writeln(k);
  for i:=w+1 to w*2 do if (a[i]>-1) and (a[i]<k) then k:=a[i];
//  if k=0 then write(-1) else write(k);
  write(k);
end.