foo.cc: In function 'int main()':
foo.cc:44:59: error: unable to find numeric literal operator 'operator""day'
   44 |                         sum=31+28+31+30+31+30+31+31+30+31+30day;
      |                                                           ^~~~~
foo.cc:44:59: note: use '-fext-numeric-literals' to enable more built-in suffixes
foo.cc:49:29: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   49 |                 if(year%4==0&&year%100!=0||year%400==0)
      |                    ~~~~~~~~~^~~~~~~~~~~~~

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