/in/foo.cc: In function 'int main()':
/in/foo.cc:25:6: warning: unused variable 'midd' [-Wunused-variable]
  int midd=(n+1)/2;
      ^~~~
/in/foo.cc:26:11: error: 'i' was not declared in this scope
  s+=abs(a[i]-midd);
           ^
/in/foo.cc:26:14: error: 'midd' was not declared in this scope
  s+=abs(a[i]-midd);
              ^~~~