ment.getElementById('main'));
                var itemStyle = {
                    normal: {
                        opacity: 0.8,
                        shadowBlur: 10,
                        shadowOffsetX: 0,
                        shadowOffsetY: 0,
                        shadowColor: 'rgba(0, 0, 0, 0.5)'
                    }
                };

                var sizeFunction = function (x) {
                    var y = Math.sqrt(x / 5e8) + 0.1;
                    return y * 40;
                }