write a program called countLowerCase

the program should read a string from the user

it should then output the number of letters in lower case

but it should count each lower case letter only once $($see examples$)$

all the code for your solution should be in a single file: the only file that is going to be tested is countLowerCase.py

you can only use what we have covered from ch$1$ to ch$7$

Examples

$\%$ python$3$ countLowerCase.py

enter a sentence: abcdefgh

number of different lower case letters found: $8$

$\%$ python$3$ countLowerCase.py

enter a sentence: ABCDEFGH

number of different lower case letters found: $0$

$\%$ python$3$ countLowerCase.py

enter a sentence: XXXXaXXXXaXXXXaaXXXXaaa

number of different lower case letters found: $1$

$\%$ python$3$ countLowerCase.py

enter a sentence: ABccDEeeeFGHIJjjjjKLMNOPpQRSTUVWXYZ

number of different lower case letters found: $4$

$\%$

HINT

keep track of the lower case letters you count.