foo.c: In function 'calculateFactorialDigits':
foo.c:12:35: error: 'M_PI' undeclared (first use in this function)
   12 |     double digitCount = log10(2 * M_PI * n) / 2 + n * log10(n / M_E) + 1;
      |                                   ^~~~
foo.c:12:35: note: each undeclared identifier is reported only once for each function it appears in
foo.c:12:65: error: 'M_E' undeclared (first use in this function)
   12 |     double digitCount = log10(2 * M_PI * n) / 2 + n * log10(n / M_E) + 1;
      |                                                                 ^~~

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