function f(){
    a.clientTop && a.clientTop, a.clientTop === !0; //$Alert
    a && a.clientTop;
    a.clientTop, a.clientTop;
    if(a) return a.clientTop && a.clientTop, a.clientTop === !0;
    if(b) return b && (b.clientTop, b.clientTop && b.clientTop), null;
}