var $win = $(window);
$('.inp').on('keydown', function (e) {
switch (e.which) {
case 38:
var top = $win.scrollTop();
top -= 10;
$win.scrollTop(top);
break;
case 40:
var top = $win.scrollTop();
top += 10;
$win.scrollTop(top);
break;
}
});