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Problems

Square string

Square string

Time limit 1 second
Memory limit 128 MiB

The string s is a square if it has the form AA, where A is some non-empty string. In other words, a square is a string that is a concatenation of two copies of the same non-empty string. For example, the strings "aa", "zqzq" and "treetree" are squares.

Determine if the given string is a square string.

Input data

One string of length no more than 100.

Output data

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

Examples

Input example #1
treetree
Output example #1
yes
Input example #2
aaa
Output example #2
no