다름이 아니라 이런경우는 어찌해야 할까요??

num  를 묶어서    num  이렇게 만들수있을까요?
1                              1
1                              3
3                              2
2                              1
2                              2
1                              5
2
5
5

그룹바이 쓰면 밑에숫자까지 다 합쳐져서 문제드라구요

도움 부탁드립니다