/in/foo.cc: In function 'int main()':
/in/foo.cc:9:17: error: 'sum' was not declared in this scope
    9 |                 sum+=v[i];
      |                 ^~~
/in/foo.cc:12:27: error: 'sum' was not declared in this scope
   12 |                 for(int j=sum;j>=v[i];j--){
      |                           ^~~
/in/foo.cc:16:24: error: 'sum' was not declared in this scope
   16 |         for(int i=1;i<=sum;i++){
      |                        ^~~