/in/foo.cc: In function 'int main()':
/in/foo.cc:21:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < a.size()-1; i++)
                  ~~^~~~~~~~~~~~
/in/foo.cc:22:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < a.size()-1 - i; j++)
                   ~~^~~~~~~~~~~~~~~~
/in/foo.cc:25:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 1; i < a.size() - 1; i++)
                  ~~^~~~~~~~~~~~~~
/in/foo.cc:29:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int j = i + 1; j <= a.size() - 1; j++)
                        ~~^~~~~~~~~~~~~~~
/in/foo.cc:36:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i <= a.size() - 6; i++)
                  ~~^~~~~~~~~~~~~~~
/in/foo.cc:39:7: warning: unused variable 'p' [-Wunused-variable]
   int p = 0;
       ^