sub a{$c+=print"? @_\n";<>}
$|=1;
$l=98,$r=1e9-1if$f=a(99)>0;
$f&&($%<0?(--$l,$r=$m-2):($l=$m,--$r))while$%=a($m=$l+$r>>1);
print'! ',$m+$c-1