foo.cc: In function 'int main()':
foo.cc:9:6: error: 'x' was not declared in this scope
    9 |   if(x%1==0)
      |      ^
foo.cc:5:8: warning: unused variable 'sum' [-Wunused-variable]
    5 |  int a,sum=0 ;
      |        ^~~

[Hydro](https://hydro.ac)提供评测服务