/in/foo.cc: In function 'int main()':
/in/foo.cc:69:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~
/in/foo.cc:80:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (ri i = 0; i < n; i++)
                  ~~^~~
/in/foo.cc:88:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~
/in/foo.cc:105:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~
/in/foo.cc:116:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (ri i = 0; i < n; i++)
                  ~~^~~
/in/foo.cc:124:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (ri i = 0; i < n; i++)
                 ~~^~~