/in/foo.cc: In function 'int main()':
/in/foo.cc:44:38: error: unable to find numeric literal operator 'operator""day'
    sum=31+28+31+30+31+30+31+31+30+31+30day;
                                      ^~~~~
/in/foo.cc:44:38: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes
/in/foo.cc:49:15: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(year%4==0&&year%100!=0||year%400==0)
      ~~~~~~~~~^~~~~~~~~~~~~