foo.cc: In function ‘int main()’:
foo.cc:20:25: warning: ‘zhongjiancha’ may be used uninitialized [-Wmaybe-uninitialized]
   20 |             zhongjiancha+=a[i];
      |             ~~~~~~~~~~~~^~~~~~
foo.cc:7:23: note: ‘zhongjiancha’ was declared here
    7 |             month,day,zhongjiancha,cha;cin>>month>>day;
      |                       ^~~~~~~~~~~~