Upper or Lower Case

Return the smallest number of steps it takes to convert a string entirely into uppercase or entirely into lower case, whichever takes the fewest number of steps. A step consists of changing one character from lower to upper case, or vice versa.

Examples

steps_to_convert("abC") ➞ 1
# "abC" converted to "abc" in 1 step

steps_to_convert("abCBA") ➞ 2
# "abCBA" converted to "ABCBA" in 2 steps

steps_to_convert("aba") ➞ 0

steps_to_convert("abaCCC") ➞ 3

Notes

• Return 0 if empty string.
• Return 0 if the string is already entirely in one case.
• Only alphabetic characters.
• Input has no spaces.