foo.cc: In function ‘int main()’:
foo.cc:7:20: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
    7 |         if (y%4==0 && y%100!=0 || y%400==0)
      |             ~~~~~~~^~~~~~~~~~~
foo.cc:21:36: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
   21 |                         if (y%4==0 && y%100!=0 || y%400==0)
      |                             ~~~~~~~^~~~~~~~~~~