foo.cc: In function ‘int main()’:
foo.cc:41:45: warning: ‘ans’ may be used uninitialized [-Wmaybe-uninitialized]
   41 |                                 else    ans += 30;
      |                                         ~~~~^~~~~
foo.cc:5:31: note: ‘ans’ was declared here
    5 |         int year, month, day, ans;
      |                               ^~~