input:<exp>a+b+&beta;</exp><br>
output:<exp><it>a</it>+<it>b</it>+&beta;</exp><br>

##</code><code>##

input:<exp>2a+&alpha;-b2</exp><br>
output:<exp>2<it>a</it>+&alpha;-<it>b</it>2</exp><br>