foo.cc: In function 'int main()':
foo.cc:16:8: warning: iteration 99999997 invokes undefined behavior [-Waggressive-loop-optimizations]
   16 |   a[i] = (a[i - 1] + a[i - 2]) % 1000007;
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:14:20: note: within this loop
   14 |  for (int i = 3; i <= 100000000; i++)
      |                  ~~^~~~~~~~~~~~

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