/in/foo.cc: In function 'int main()':
/in/foo.cc:68:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~
/in/foo.cc:79:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (ri i = 0; i < n; i++)
                  ~~^~~
/in/foo.cc:87:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~
/in/foo.cc:104:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~
/in/foo.cc:115:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (ri i = 0; i < n; i++)
                  ~~^~~
/in/foo.cc:123:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~