Vlad and a Pair of Numbers

ÌâÄ¿Á´½Ó ÌâÄ¿ÃèÊö£º Vlad found two positive numbers $a$ and $b(a,b>0)$. He discovered that $a¨’b=\frac{a+b}{2}$, where $¨’$ means the bitwise exclusive OR , and