foo.cc: In function 'int WeekdayOfTheFirstDay(int, int)':
foo.cc:21:1: warning: no return statement in function returning non-void [-Wreturn-type]
   21 | }
      | ^
foo.cc: In function 'int main()':
foo.cc:25:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   25 |  scanf("%d %d",&year,&month);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~

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