text: #include <iostream>
  
  int main() {
      int a_len=20;
      int a[a_len];
      for (int i=0; i<a_len; i++){
          a[i] = i;
      }
  
      a_len /= 2;
      for (int i=1; i<a_len; i++) {
          int tmp = a[i];
          int y;
          for(y=i; y<a_len; y++) {
              a[y] = a[y+1];
          }
          a[a_len-1] = a[a_len-1+i];
          a[a_len-1+i] = tmp;
  
      }
  
      for (const auto& e : a) {
          std::cout << e << std::endl;
      }
  
      return 0;
  }