PROGRAMMING:Huffman coding
###Input format:
There is only one line, which is a string composed of lower case English letters no more than 255 characters in length.
###Output format:
There are several lines, each line is composed of two parts: a letter and the frequency of the letter, separated by a space, and arranged according to the frequency, when the frequency is the same, it is arranged according to the order of the ASCII code of the letter.
###Input example:
```in
soon
```
###Output example:
```out
o 2
n 1
s 1
```
answer：If there is no answer, please comment
###Input format:
There is only one line, which is a string composed of lower case English letters no more than 255 characters in length.
###Output format:
There are several lines, each line is composed of two parts: a letter and the frequency of the letter, separated by a space, and arranged according to the frequency, when the frequency is the same, it is arranged according to the order of the ASCII code of the letter.
###Input example:
```in
soon
```
###Output example:
```out
o 2
n 1
s 1
```
answer：If there is no answer, please comment