foo.cc: In function ‘int f(int, int, int)’:
foo.cc:8:18: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
    8 |         if(a%4==0&&a%100!=0||a%400==0)
      |            ~~~~~~^~~~~~~~~~
foo.cc:11:20: warning: ‘ans’ may be used uninitialized [-Wmaybe-uninitialized]
   11 |                 ans+=mon[i];
      |                 ~~~^~~~~~~~
foo.cc:7:13: note: ‘ans’ was declared here
    7 |         int ans;
      |             ^~~