foo.cc: In function 'LL F(LL)':
foo.cc:19:24: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   19 |             res2 = F(i + 1 >> 1);
      |                      ~~^~~
foo.cc:22:24: warning: suggest parentheses around '-' inside '>>' [-Wparentheses]
   22 |             res1 = F(i - 2 >> 1);
      |                      ~~^~~
foo.cc: In function 'int main()':
foo.cc:33:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   33 |     scanf("%lld", &n);
      |     ~~~~~^~~~~~~~~~~~

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