PROGRAMMING:Judging the structure of the beginning and end of a string

Enter a string to determine whether the head and tail correspond. For example, the string 'abcba' corresponds to the beginning and the end. For example, the string '+ - * - +' also corresponds to the beginning and end. For example, the string 'abcbb' does not correspond to the beginning and end.
###Input format:
Enter a string
###Output format:
If the head and tail correspond, output 'yes'
Otherwise output 'no'
###Input example:
```in
abcba
```
###Output example:
```out
yes
```







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