/in/foo.cc: In function 'void Dfs(int, int, int, int, int)':
/in/foo.cc:49:6: warning: unused variable 'pre' [-Wunused-variable]
  int pre=-1;
      ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:151:6: warning: unused variable 'Sizze' [-Wunused-variable]
  int Sizze=40<<20;//40M
      ^~~~~