/in/foo.c: In function 'main':
/in/foo.c:45:5: warning: operation on 'q' may be undefined [-Wsequence-point]
    q=(++q)%m;
    ~^~~~~~~~
/in/foo.c:53:6: warning: operation on 'p' may be undefined [-Wsequence-point]
     p=p++%n;
     ~^~~~~~
/in/foo.c:14:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j;
        ^