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:=5001;c:=10001;
for i:=1 to g do
    begin
     readln(f,a,b);
     if (a<=min) and (a>=w) then
        begin
         if min<>a then
         begin
         min:=a;
         c:=b;
         end;
         if b<c then c:=b;
        end;
    end;
if min>=w then write(e,c) else write(e,'-1');
close(f);close(e);
END.