/in/foo.cc: In function 'int main()':
/in/foo.cc:11:3: error: expected primary-expression before 'else'
   11 |   else
      |   ^~~~
/in/foo.cc:12:23: error: 'i' was not declared in this scope
   12 |           for(int i=a;i<=b;i++)
      |                       ^
/in/foo.cc:7:13: warning: unused variable 'n' [-Wunused-variable]
    7 |         int n=0;
      |             ^