/in/foo.cc: In function 'int main()':
/in/foo.cc:12:35: warning: iteration 36u invokes undefined behavior [-Waggressive-loop-optimizations]
   sum[i] = sum[i - 1] + sum[i - 3];
                                   ^
/in/foo.cc:11:20: note: containing loop
  for (int i = 5; i <= 41; i++) {
                    ^