/in/foo.cc:49:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:75:6: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
   if (fa[fx][0]&&(dis[x]-dis[fa[fx][0]])*2==tmp)
      ^