https://www.youtube.com/watch?v=W_VNm0uffBM
Similar to -뿐이다. This is more formal and less common. Tends to get used in emotional contexts, despite being similar to 뿐이다.

이걸 혼자 다 했다니 놀라울 따름이네요. / To find that you did this all by yourself, I have nothing but surprise.