foo.cc: In function 'int IsLeapYear(int)':
foo.cc:4:20: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    4 |  if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
      |      ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
foo.cc: In function 'int DaysOfMonth(int, int)':
foo.cc:28:1: warning: control reaches end of non-void function [-Wreturn-type]
   28 | }
      | ^

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