program energie;
var w,i,g,cmin:integer;
e,c:array[1..5000] of integer;
    f,r:text;
begin
assign(f,'energii.in');
reset(f);
assign(r,'energii.out');
rewrite(r);
read(f,g);
read(f,w);
cmin:=10000;
 for i:=1 to g do
    begin
    read(f,e[i],c[i]);
        if (e[i]>=w)and(c[i]<=cmin) then cmin:=c[i];
    end;
if cmin<>10000 then write(r,cmin)
else write(r,-1);
close(f);close(r);
end.