When <tt>input = [ n i<sub>1</sub> &hellip; i<sub>n</sub> ]</tt> is set before
calling this command, then

<p>
mark all atoms <i>i</i> = <tt>i<sub>1</sub>, &hellip; , i<sub>n</sub>$ 
with <tt>fixed[i] = 1</tt>.

