foo.cc: In function 'int isLeap(int)':
foo.cc:7:25: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    7 |  if (y%400==0 || y%4==0 && y%100!=0)
      |                  ~~~~~~~^~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:27:36: warning: unused variable 'LastMonthDay' [-Wunused-variable]
   27 |  int y1, m1, d1, y2, m2, d2, days, LastMonthDay;
      |                                    ^~~~~~~~~~~~

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