foo.cc: In function 'int main()':
foo.cc:11:19: warning: unused variable 'j' [-Wunused-variable]
  int year,month,i,j;
                   ^
foo.cc: In function 'int isleapyear(int)':
foo.cc:46:27: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(year%400==0||year%4==0&&year%100!=0)
                  ~~~~~~~~~^~~~~~~~~~~~~

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