PROGRAMMING:Calculate the days of the month

Enter the year and month, output the days of the month. Note: January, March, may, July, August, October and December are 31 days, April, June, September and November are 30 days, for February, leap year is 29 days, non leap year is 28 days. The standard of judging leap year: the year that can be divided by 4 but not 100, or the year that can be divided by 400 is leap year.
###Input format:
Enter the year and month, separated by a space, for example: "2009 5".
###Output format:
Output the number of days in the month, such as: "31"
###Input example:
Here is a set of inputs. For example:
```in
2009 12
```
###Output example:
The corresponding output is given here. For example:
```out
thirty-one
```
###Input example:
Here is a set of inputs. For example:
```in
2000 2
```
###Output example:
The corresponding output is given here. For example:
```out
twenty-nine
```
###Input example:
Here is a set of inputs. For example:
```in
2000 14
```
###Output example:
The corresponding output is given here. For example:
```out
Error
```







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