/in/foo.cc: In function 'int main()':
/in/foo.cc:11:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for (int i = 2; i < n; i++)
  ^~~
/in/foo.cc:18:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   for (int i = 0; i < a.size(); i++)
   ^~~
/in/foo.cc:18:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < a.size(); i++)
                   ~~^~~~~~~~~~