PROGRAMMING:mm-dd-yyyy to yyyy-mm-dd

American usually use day-month-year, but Chinese often use year-month-day. Please write a program to transfer the
date from American style to Chinese style.
### Input format:
mm-dd-yyyy
### Output format:
yyyy-mm-dd
### Input sample:
```
06-08-2017
```
### Output sample:
```
2017-06-08
```






answer：If there is no answer, please comment