foo.cc: In function 'int isleapyear(int)':
foo.cc:5:14: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    5 |  if(year%4==0&&year%100!=0||year%400==0)
      |     ~~~~~~~~~^~~~~~~~~~~~~
foo.cc: At global scope:
foo.cc:47:40: error: ISO C++ forbids declaration of 'weekdayofthefirstday' with no type [-fpermissive]
   47 | weekdayofthefirstday(int year,int month)
      |                                        ^

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