foo.cc: In function ‘int leap(int)’:
foo.cc:5:23: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
    5 |         return (y%4==0&&y%100!=0||y%400==0);
      |                 ~~~~~~^~~~~~~~~~
foo.cc: In function ‘int main()’:
foo.cc:25:19: warning: variable ‘mod’ set but not used [-Wunused-but-set-variable]
   25 |         int y,m,d,mod,mod1,days=10000;
      |                   ^~~
foo.cc:25:23: warning: unused variable ‘mod1’ [-Wunused-variable]
   25 |         int y,m,d,mod,mod1,days=10000;
      |                       ^~~~