var g,w,min,a,b,i,c:integer;
    f,e:text;
BEGIN
assign(f,'energii.in');reset(f);assign(e,'energii.out');rewrite(e);
read(f,g);read(f,w);min:=-1;
for i:=1 to g do
    begin
     readln(f,a,b);
     if a>=w then
        begin
         if min<>a then
            begin
             min:=a;
             c:=b;
            end;
         if b<c then c:=b;
        end;
     end;
if min>=2 then write (e,c) else write (e,-1);
close(f);close(e);
END.