var e,c:array[1..1001]of integer;
    n,p,i,t,l,k:integer;
    r:array[1..1001]of real;
    max:real;
    f,g:text;

begin
assign(f,'energii.in');
reset(f);
assign(g,'energii.out');
rewrite(g);
readln(f,n);
readln(f,t);
for i:=1 to n do begin
   readln(f,e[i],c[i]);
   if c[i]=0 then r[i]:=1000*1000
             else r[i]:=e[i]/c[i];
end;
l:=0;
while l=0 do begin
   max:=-1;
   for i:=1 to n do
      if r[i]>max then begin
                       max:=r[i];
                       p:=i;
                       end;
   if max=-1 then l:=2;
   if t>e[p] then begin
                  t:=t-e[p];
                  k:=k+c[p];
                  e[p]:=-2;
                  c[p]:=-2;
                  r[p]:=-2;
                  end
             else if t=e[p] then begin
                                 l:=1;
                                 k:=k+c[p];
                                 end
                            else l:=2;
end;
if l=2 then begin
            p:=9999;
            for i:=1 to n do if (t<e[i]+1)and(c[i]<p) then p:=c[i];
            k:=k+p;
            end;
if p=9999 then write(g,'-1')
          else write(g,k);
close(g);
end.