/in/foo.cc: In function 'void dfs(int, int, int, int)':
/in/foo.cc:38:8: warning: unused variable 'xx' [-Wunused-variable]
    int xx = ans.back();
        ^~
/in/foo.cc:54:18: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   if(found = true)
                  ^
/in/foo.cc:52:7: warning: unused variable 'tt' [-Wunused-variable]
   int tt = tmpt.back();
       ^~