foo.cc:30:42: error: ISO C++ forbids declaration of 'WeekdayOfTheFirstDay' with no type [-fpermissive]
   30 |  WeekdayOfTheFirstDay(int year,int month )
      |                                          ^
foo.cc: In function 'int WeekdayOfTheFirstDay(int, int)':
foo.cc:39:10: warning: left operand of comma operator has no effect [-Wunused-value]
   39 |   return 0,ddday;
      |          ^

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