How to get arabic numerals at all levels of a nested list?

1. lorem ipsum
2. dolor sit
   1. ⟵ this should be 1, not i
   2. ⟵ this should be 2, not ii
   3. ⟵ this should be 3, not iii
      1. ⟵ this should be 1, not a
      2. ⟵ this should be 2, not b
      3. ⟵ this should be 3, not c
      4. ⟵ this should be 4, not d
         1. ⟵ this should be 1, not a
         2. ⟵ this should be 2, not b
         3. ⟵ this should be 3, not c
         4. ⟵ this should be 4, not d
   4. ⟵ this should be 4, not iv
   5. ⟵ this should be 5, not v
3. amet consectetur
4. adipiscing elit