/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<e[x].size();i++)
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'void dfs1(int)':
/in/foo.cc:22:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<e[x].size();i++)
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'void dfs2(int, int)':
/in/foo.cc:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<e[x].size();i++)
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'int calc(int, int)':
/in/foo.cc:48:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:15:11: warning: iteration 19 invokes undefined behavior [-Waggressive-loop-optimizations]
   fa[x][i]=fa[fa[x][i-1]][i-1];
   ~~~~~~~~^~~~~~~~~~~~~~~~~~~~
/in/foo.cc:14:15: note: within this loop
  for(int i=1;i<=20;i++)
              ~^~~~