Maximum( obj1, obj2.. ) 
Maximum( list )
Maximum returns  the  maximum of  its  arguments,  i.e.,  that argument
obj_i for  which  obj_k <= obj_i for all  k.   In its second  form
Maximum takes  a list list and returns the maximum of the elements of
this list.
Typically the arguments  or elements  of the  list  respectively will  be
integers, but actually they  can be  objects of an arbitrary  type.  This
works because any two objects can be compared using the < operator.
    gap> Maximum( -123, 700, 123, 0, -1000 );
    700
    gap> Maximum( [ -123, 700, 123, 0, -1000 ] );
    700
    gap> Maximum( [ 1, 2 ], [ 0, 15 ], [ 1, 5 ], [ 2, -11 ] );
    [ 2, -11 ]        # lists are compared elementwise 
GAP 3.4.4