/in/foo.cc: In function 'void init()':
/in/foo.cc:9:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < pre.size(); i++)
                  ~~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:76:22: error: 'pow' was not declared in this scope
  cout << pow(2, count);
                      ^