foo.cc: In function 'int IsLeapYear(int)':
foo.cc:4:14: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    4 |  if(year%4==0&&year%100!=0||year%400==0)
      |     ~~~~~~~~~^~~~~~~~~~~~~
foo.cc: At global scope:
foo.cc:20:40: error: ISO C++ forbids declaration of 'WeekdayOfTheFirstDay' with no type [-fpermissive]
   20 | WeekdayOfTheFirstDay(int year,int month){
      |                                        ^
foo.cc: In function 'int main()':
foo.cc:28:10: warning: unused variable 'd' [-Wunused-variable]
   28 |  int y,m,d;
      |          ^

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