/in/foo.cc: In function 'int main()':
/in/foo.cc:16:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i <=t1.size(); i++)
                  ~~^~~~~~~~~~~
/in/foo.cc:20:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int j = 1; j <= t2.size(); j++)
                  ~~^~~~~~~~~~~~
/in/foo.cc:23:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 1; i <= t1.size(); i++)
                   ~~^~~~~~~~~~~~