foo.cc: In function ‘int main()’:
foo.cc:9:21: warning: ‘a’ may be used uninitialized [-Wmaybe-uninitialized]
    9 |                 if(i%a!=0)
      |                    ~^~
foo.cc:5:15: note: ‘a’ was declared here
    5 |         int n,a;
      |               ^