foo.cc: In member function 'void Splay::splay(int)':
foo.cc:30:31: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
         for (int f = fa[k]; f = fa[k]; rotate(k)) {
                             ~~^~~~~~~
foo.cc: In function 'int main()':
foo.cc:140:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &n, &mn);
     ~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:144:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("\n%c %d", &op, &k);
         ~~~~~^~~~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。