Exchange the levels of the MultiIndex so the index is (numbers, letters), then ensure it is sorted. Return the new Series.

Input

A  0     0
   1     1
   2     2
   3     3
   4     4
        ..
C  5    25
   6    26
   7    27
   8    28
   9    29
Length: 30, dtype: int64

Output

0  A     0
   B    10
   C    20
1  A     1
   B    11
        ..
8  B    18
   C    28
9  A     9
   B    19
   C    29
Length: 30, dtype: int64