function show_blocks(el) {
    [2,3,4,5,6,7,8,9,10].forEach(function(i){
        $('#block'+i).hide();
    });
    var val = $(el).val();

    var blocks = {
        3: 5,
        4: 6,
        5: 7,
        6: 8,
        7: 9,
        30: 10
    };
    $('#block' + blocks[val]).show();
    if (3 == val) {
        $('#block2').show();
    }
}