PROGRAMMING:Number seven game

The number seven game is a common drinking order, that is, many people in a circle, starting with one person calling a number, and the people behind them in turn + 1 report the number. If they encounter a number containing 7 or a multiple of 7, they have to call pass. Enter two positive integers m, n (1 < = m < = n), please count the times of calling pass between [M-N].
###Input format:
Enter two positive integers m, n (1 < = m < = n), separated by commas
###Output format:
The number of times to call pass between output [M-N]. If not, output none
###Input sample 1:
```in
10,21
```
###Output sample 1:
```out
three
```
###Input sample 2:
```in
10,13
```
###Output sample 2:
```out
None
```






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