/in/foo.cc: In function 'int solve2(int)':
/in/foo.cc:51:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < v.size(); i++)
                  ~~^~~~~~~~~~
/in/foo.cc:74:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < v.size(); i++)
                  ~~^~~~~~~~~~
/in/foo.cc:78:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = i + 1; j < v.size(); j++)
                       ~~^~~~~~~~~~
/in/foo.cc:99:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < v.size(); i++)
                  ~~^~~~~~~~~~
/in/foo.cc:114:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < v.size() / 2; i++)
                  ~~^~~~~~~~~~~~~~
/in/foo.cc:119:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int j = v.size() - 1; j >= v.size() / 2; j--)
                             ~~^~~~~~~~~~~~~~~