foo.cc: In function 'int main()':
foo.cc:6:19: warning: variable 'q' set but not used [-Wunused-but-set-variable]
  int n,a,x,xx,m=0,q,w;
                   ^
foo.cc:6:21: warning: variable 'w' set but not used [-Wunused-but-set-variable]
  int n,a,x,xx,m=0,q,w;
                     ^
foo.cc:22:12: warning: 'xx' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<xx<<" "<<x;
            ^~~