import re
s=""""Заключение:
1
2
3
Подпись"""
print(re.search(r'(?m)^(\d[\d\s]*)^Подпись', s).group(1).split())
aW1wb3J0IHJlCnM9IiIiItCX0LDQutC70Y7Rh9C10L3QuNC1OgoxCjIKMwrQn9C+0LTQv9C40YHRjCIiIgpwcmludChyZS5zZWFyY2gocicoP20pXihcZFtcZFxzXSopXtCf0L7QtNC/0LjRgdGMJywgcykuZ3JvdXAoMSkuc3BsaXQoKSk=