Distinguishing between crows and magpies in the Korean countryside

In the early morning, when walking in the rural areas of Korea, you can often see large black birds sitting on streetlights, making loud 'caw caw' sounds. I became curious whether these birds are crows or large magpies (ravens). I would like to know if such large birds can also be frequently seen in the Korean countryside. Are there any tips that could help distinguish between these types of birds? If there are any special methods to easily identify crows and large magpies in Korea, please share them. Additionally, I am curious whether these birds can be seen in urban areas like Gangnam or Itaewon in Seoul. Observing birds in various environments seems like it could help better understand their characteristics.