/in/foo.cc: In function 'int main()':
/in/foo.cc:29:41: warning: operation on 'start' may be undefined [-Wsequence-point]
   29 |                         if (j > 0) start=(++start)%m;
      |                                    ~~~~~^~~~~~~~~~~~
/in/foo.cc:29:41: warning: operation on 'start' may be undefined [-Wsequence-point]