var num = 1;

$( "button" ).on( "click", function() {

if( num === 1) {

num++;
$( "<div />" ).attr( "id", num ).text( "Content-" + num ).appendTo( $( ".inner" ) );
return;
}

if( num === 2) {

num--;
$( "<div />" ).attr( "id", num ).text( "Content-" + num ).appendTo( $( ".inner" ) );
return;
}

if( num === 3) {

num--;
$( "<div />" ).attr( "id", num ).text( "Content-" + num ).appendTo( $( ".inner" ) );
return;
}

});