PROGRAMMING:Count the number of times each character occurs in a string

Read a string, count the number of occurrences of each character in the string, and output the number of occurrences in descending order.
### Input Format:
### Output Format:
### Sample Inputs:
```in
This is a good idea.
```
### Sample Output:
```out
: 4
i : 3
s : 2
a : 2
o : 2
d : 2
T : 1
h : 1
g : 1
e : 1
. : 1
```







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