foo.cc: In function 'int main()':
foo.cc:15:14: warning: unused variable 'i' [-Wunused-variable]
   15 |     for (int i = 0; n >= 0; n--)
      |              ^
foo.cc:14:9: warning: unused variable 'i' [-Wunused-variable]
   14 |     int i = 0;
      |         ^

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