/in/foo.cc: In function 'int main()':
/in/foo.cc:12:25: error: 'sum' was not declared in this scope
   12 |                         sum+=a%10;
      |                         ^~~
/in/foo.cc:15:20: error: 'sum' was not declared in this scope
   15 |                 if(sum%7==0)
      |                    ^~~