/in/foo.cc: In constructor 'node::node(int, ll, int, int)':
/in/foo.cc:27:5: warning: 'node::val' will be initialized after [-Wreorder]
  ll val;
     ^~~
/in/foo.cc:26:9: warning:   'int node::cap' [-Wreorder]
  int to,cap,rev;
         ^~~
/in/foo.cc:28:2: warning:   when initialized here [-Wreorder]
  node(int to=0,ll val=0,int cap=0,int rev=0):to(to),val(val),cap(cap),rev(rev){}
  ^~~~
/in/foo.cc: In function 'bool spfa()':
/in/foo.cc:39:13: warning: unused variable 'head' [-Wunused-variable]
  static int head,tail;
             ^~~~
/in/foo.cc:39:18: warning: unused variable 'tail' [-Wunused-variable]
  static int head,tail;
                  ^~~~
/in/foo.cc: In function 'll maxflow()':
/in/foo.cc:82:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^