Finding smax of a discontinuous function

Hi, I am new to GAMS but I am trying to use this MTSP formulation:
http://yetanothermathprogrammingconsultant.blogspot.com/2009/03/mtspvrp-example.html
However for the purposes I want to use it for, rather than trying to minimize the total tour length, I want to minimize the maximum tour length:

cost.. z =e= sum(arcs, c(arcs)*x(arcs));

Changing sum to smax here doesn’t seem to work here because of x(arcs) being a binary variable. Is there a way to rewrite this so it will work?