/in/foo.cc: In function 'int dfs(int, int, int, int)':
/in/foo.cc:63:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'int lca_min(int, int)':
/in/foo.cc:67:6: warning: variable 're' set but not used [-Wunused-but-set-variable]
  int re;
      ^~
/in/foo.cc:96:9: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
  ans=min(ans,minn[y][j]);
      ~~~^~~~~~~~~~~~~~~~