uses crt;
type vector=array[1..20000]of longint;
var f,h:text;
    G,W,i,p,y:longint;
    E,C:vector;
procedure cmin(i,j:longint;var p:longint);
var p1:longint;
 begin
  if i=j then
       begin
       if E[i]>=W then p:=C[i]
                  else p:=-1;
       end;
  if i<j then
      begin
      if E[i]>=W then p:=C[i]
                 else p:=-1;
      cmin(i+1,j,p1);
      if (p1=-1)and(p=-1) then p:=-1;
      if (p1<>-1)and(p=-1) then p:=p1;
      if (p1<>-1)and(p<>-1) then if p1<=p then p:=p1;

     end;
  end;
begin
clrscr;
assign(f,'energii.in');
reset(f);
read(f,G);
read(f,W);
for i:=1 to G do
    begin
    read(f,E[i]);
    read(f,C[i]);
    end;
close(f);
cmin(1,G,p);
assign(h,'energii.out');
rewrite(h);
write(h,p);
close(h);
end.