var n,i,j,w,x,y,p,x1,aux:integer;
    f,g:text;
    a,b:array[0..5001]of longint;
begin
assign(f,'energii.in');reset(f);assign(g,'energii.out');rewrite(g);
read(f,n,w);  p:=0;
for i:=1 to n do
  begin
     read(f,x,y);
     if (y<a[x])or(a[x]=0) then begin a[x]:=y; p:=p+1; b[p]:=x; end;
     j:=1;
     while j<=p do
       begin
         aux:=x+b[j]; x1:=b[j];
         if aux<=w then if a[aux]<>0 then begin if a[aux]>a[x1]+y then a[aux]:=a[x1]+y; end
                                     else begin a[aux]:=a[x1]+y; p:=p+1; b[p]:=aux; end;
         j:=j+1;
       end;
  end;
if a[w]<>0 then write(g,a[w]) else write(g,-1);
close(f);close(g);
end.