/in/foo.cc: In function 'int main()':
/in/foo.cc:29:9: warning: unused variable 'q' [-Wunused-variable]
    node*q=head;
         ^
/in/foo.cc:12:6: warning: unused variable 'a' [-Wunused-variable]
  int a[10000]={0};
      ^
/in/foo.cc:23:6: warning: unused variable 'i' [-Wunused-variable]
  int i=0;int t=1;
      ^