Square string#8697

Square string

1 second

128 megabytes

Very easy

A string $s$ is called square if it has the form $AA$ , where $A$ is a non-empty string. In other words, a square string is obtained by concatenating two copies of the same non-empty string.

For example, the strings " $aa$ ", " $z q z q$ zqzq", and " $t r ee t r ee$ treetree" are square.

Determine whether the given string is square.

Input

A string is given, containing no more than $100$ characters.

Output

Print "yes" if the input string is square, and "no" otherwise.

Examples

Example 1

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Example 2

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z q z q

t r ee t r ee